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An EEG recording cap being used on a participant in a brain wave study.
.Electroencephalography (EEG) is the recording of electrical activity along the scalp produced by the firing of neurons within the brain.^ Behavior and brain electrical activity.
  • James D. Frost, Jr., M.D. - Neurology Faculty - Baylor College of Medicine, Houston, Texas 19 January 2010 18:39 UTC www.bcm.edu [Source type: Academic]

^ Electrocephalograms (EEGs) are recordings of the electrical potentials in the brain.

^ Magnetoencephalography: Recording brain activities.
  • I-LABS: Toshiaki Imada, Ph.D. - Publications 19 January 2010 18:39 UTC ilabs.washington.edu [Source type: Academic]

[1] .In clinical contexts, EEG refers to the recording of the brain's spontaneous electrical activity over a short period of time, usually 20–40 minutes, as recorded from multiple electrodes placed on the scalp.^ Behavior and brain electrical activity.
  • James D. Frost, Jr., M.D. - Neurology Faculty - Baylor College of Medicine, Houston, Texas 19 January 2010 18:39 UTC www.bcm.edu [Source type: Academic]

^ The recording electrodes are positioned on the scalp and their integrated output displays the rhythmic activity of the brain.

^ Electrocephalograms (EEGs) are recordings of the electrical potentials in the brain.

.In neurology, the main diagnostic application of EEG is in the case of epilepsy, as epileptic activity can create clear abnormalities on a standard EEG study.^ Across a large number of EEG and QEEG studies, there is a broad consensus that schizophrenia shows a high incidence of EEG and QEEG abnormalities.
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

^ Mood Disorders: Anxiety, Panic, Obsessive-Compulsive, and Eating Disorders Several studies suggest a high incidence of EEG abnormalities in patients with anxiety disorders, panic disorders, and obsessive-compulsive disorder (OCD).
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

^ EEG are generally used in medical diagnostics to detect electrical abnormalities in the brain due to disease (e.g., epilepsy, parkinson’s, tremors) .

[2] .A secondary clinical use of EEG is in the diagnosis of coma, encephalopathies, and brain death.^ EEG analysis can be used for monitor-ing surgical patients for depth of anesthesia, cerebral hypoxia or ischemia, for monitoring critical care patients in coma or metabolic encephalopathy, and for diagnosis of certain clinical patients or experimental animals.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ A voluminous literature attests to the robustness of conventional EEG studies and their clinical utility in disorders of brain function.
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

^ EEG are generally used in medical diagnostics to detect electrical abnormalities in the brain due to disease (e.g., epilepsy, parkinson’s, tremors) .

.EEG used to be a first-line method for the diagnosis of tumors, stroke and other focal brain disorders, but this use has decreased with the advent of anatomical imaging techniques such as MRI and CT.^ The cordance mapping techniques can be used to determine or assess the brain in accident situations or diseases such as cerebral vascular diseases or strokes which may be the result of genetic or developmental-congenital problems, traumatic head injury, exposure to toxic agents or the product of other pathogenic physiological processes such as elevated blood pressures, stress responses, and arterial blockages.
  • Determining the nature of brain lesions by electroencephalography - Patent 5269315 19 January 2010 18:39 UTC www.freepatentsonline.com [Source type: Academic]

^ Moreover, although the data used in the scoring have been obtained from absolute power values from EEG, it is possible that other values of electrical output can be used.
  • Diagnosing brain conditions by quantitative electroencephalography - Patent 5230346 19 January 2010 18:39 UTC www.freepatentsonline.com [Source type: Academic]

^ Only the cerebral cortex is represented in the EEG, other parts of the brain may influence it indirectly but do not contribute to the voltages recorded.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

.Derivatives of the EEG technique include evoked potentials (EP), which involves averaging the EEG activity time-locked to the presentation of a stimulus of some sort (visual, somatosensory, or auditory).^ Habituation of averaged evoked potentials in man.
  • Prepulse Effects as a Function of Cortical Projection System 19 January 2010 18:39 UTC rsimons.psych.udel.edu [Source type: Academic]

^ Effects of rise-time on late components of the auditory evoked potential.
  • Prepulse Effects as a Function of Cortical Projection System 19 January 2010 18:39 UTC rsimons.psych.udel.edu [Source type: Academic]
  • Two Reflexes 19 January 2010 18:39 UTC rsimons.psych.udel.edu [Source type: Academic]

^ ON and OFF components in the auditory evoked potential.
  • Steven A. Hillyard - Publications 19 January 2010 18:39 UTC sdepl.ucsd.edu [Source type: Academic]

.Event-related potentials refer to averaged EEG responses that are time-locked to more complex processing of stimuli; this technique is used in cognitive science, cognitive psychology, and psychophysiological research.^ Recent advances in event-related brain potential research (pp.
  • I-LABS: Toshiaki Imada, Ph.D. - Publications 19 January 2010 18:39 UTC ilabs.washington.edu [Source type: Academic]

^ Current trends in event-related potential research (pp.
  • Prepulse Effects as a Function of Cortical Projection System 19 January 2010 18:39 UTC rsimons.psych.udel.edu [Source type: Academic]
  • Two Reflexes 19 January 2010 18:39 UTC rsimons.psych.udel.edu [Source type: Academic]

^ Event-related potentials in cognitive science.
  • Steven A. Hillyard - Publications 19 January 2010 18:39 UTC sdepl.ucsd.edu [Source type: Academic]

Epileptic spike and wave discharges monitored with EEG.

Contents

Source of EEG activity

.The electrical activity of the brain can be described in spatial scales from the currents within a single dendritic spine to the relatively gross potentials that the EEG records from the scalp, much the same way that the economics can be studied from the level of a single individual's personal finances to the macro-economics of nations.^ The origin of action potentials can be traced to the electrical activity at the cellular level.

^ Behavior and brain electrical activity.
  • James D. Frost, Jr., M.D. - Neurology Faculty - Baylor College of Medicine, Houston, Texas 19 January 2010 18:39 UTC www.bcm.edu [Source type: Academic]

^ Electrocephalograms (EEGs) are recordings of the electrical potentials in the brain.

.Neurons, or nerve cells, are electrically active cells which are primarily responsible for carrying out the brain's functions.^ He is credited with the discovery of the spontaneous EEG in animals and with demonstrating the ability to detect electrical brain responses to stimuli.
  • Binaural Beat Stimulation Combined with Alpha Biofeedback 19 January 2010 18:39 UTC web-us.com [Source type: Academic]

^ Dawson GD: Cerebral responses to electrical stimulation of peripheral nerve in man.
  • BioMedical Engineering OnLine | Full text | On the methodological unification in electroencephalography 19 January 2010 18:39 UTC www.biomedical-engineering-online.com [Source type: Academic]

^ The invention provides for information about brain electrical function that can be associated with specific diseases and syndromes and thus can assist in determining the likelihood of certain brain diseases.
  • Diagnosing brain conditions by quantitative electroencephalography - Patent 5230346 19 January 2010 18:39 UTC www.freepatentsonline.com [Source type: Academic]

.Neurons create action potentials, which are discrete electrical signals that travel down axons and cause the release of chemical neurotransmitters at the synapse, which is an area of near contact between two neurons.^ The glial cell contribution to the EEG results from potential changes in cortical neurons which cause transient changes in extracellular K+ ; these in turn produce passive depolarizations in membrane potentials of glial cells.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ Thus they contrast with nerve or muscle action potentials in which small electrically active areas of axons or muscle fibers move toward, pass by and move away from the recording electrodes, e.g., when nerve conduction velocities are measured.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ The release of neurotransmitter at a synapse allows selective movements of ions through the postsynaptic membrane.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

.This neurotransmitter then activates a receptor in the dendrite or body of the neuron that is on the other side of the synapse, the post-synaptic neuron.^ Studies correlating surface events and intracellular events in cortical neurons show a direct relationship of post-synaptic potentials (PSPs) and surface potentials.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

.The neurotransmitter, when combined with the receptor, typically causes an electrical current within the dendrite or body of the post-synaptic neuron.^ Studies correlating surface events and intracellular events in cortical neurons show a direct relationship of post-synaptic potentials (PSPs) and surface potentials.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

Thousands of post-synaptic currents from a single neuron's dendrites and body then sum up to cause the neuron to generate an action potential (or not). This neuron then synapses on other neurons, and so on.
.EEG reflects correlated synaptic activity caused by post-synaptic potentials of cortical neurons.^ Studies correlating surface events and intracellular events in cortical neurons show a direct relationship of post-synaptic potentials (PSPs) and surface potentials.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ All-or-none action potentials in axons do not contribute significantly to the ongoing activity of the EEG. Cortical axons course in many directions relative to the surface, therefore the net effect of their action potentials on surface electrodes is zero.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ The glial cell contribution to the EEG results from potential changes in cortical neurons which cause transient changes in extracellular K+ ; these in turn produce passive depolarizations in membrane potentials of glial cells.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

.The ionic currents involved in the generation of fast action potentials may not contribute greatly to the averaged field potentials representing the EEG .^ Only the cerebral cortex is represented in the EEG, other parts of the brain may influence it indirectly but do not contribute to the voltages recorded.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ All-or-none action potentials in axons do not contribute significantly to the ongoing activity of the EEG. Cortical axons course in many directions relative to the surface, therefore the net effect of their action potentials on surface electrodes is zero.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ Furthermore, the brain electrical activity in response to specific stimuli (i.e., event-related potentials or taskactivated EEG) may be useful under some circumstances.
  • Diagnosing brain conditions by quantitative electroencephalography - Patent 5230346 19 January 2010 18:39 UTC www.freepatentsonline.com [Source type: Academic]

[3][4] .More specifically, the scalp electrical potentials that produce EEG are generally thought to be caused by the extracellular ionic currents caused by dendritic electrical activity, whereas the fields producing magnetoencephalographic signals[5] are associated with intracellular ionic currents [6].^ Eye movements often are accompanied by eyelid movements (e.g., blinking) and/or with movements of the scalp, either of which may be associated with muscle potentials and/or electrode/wire movement artifacts.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ Open interviews revealed that one subject who was certain he had found the key and was controlling his alpha was in actuality producing no more EEG alpha than before.
  • Binaural Beat Stimulation Combined with Alpha Biofeedback 19 January 2010 18:39 UTC web-us.com [Source type: Academic]

^ P50 and later potentials may be due, like blink PPI, to an active, extrinsic mechanism; that is, activity from the specific path feeds into and modulates activity in the nonspecific path.

.The electric potentials generated by single neurons are far too small to be picked by EEG or MEG.[4] EEG activity therefore always reflects the summation of the synchronous activity of thousands or millions of neurons that have similar spatial orientation, radial to the scalp.^ A single electrode records a potential from an arbitrary number of such ensembles, spatially filtered by different conductivities of cortex, dura mater, skull and scalp.
  • BioMedical Engineering OnLine | Full text | On the methodological unification in electroencephalography 19 January 2010 18:39 UTC www.biomedical-engineering-online.com [Source type: Academic]

^ The rhythms of the EEG are explained by a model in which afferent action potentials arrive in somewhat synchronous volleys at presynaptic terminals within a given area; activity in other similar areas is not necessarily synchronous therefore recordings made from different parts of the scalp differ in appearance.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ When this data is digitized and processed as in quantitative EEG ("qEEG"), it is possible to obtain topographical brain mapping of electrical activity in different brain regions.
  • Determining the nature of brain lesions by electroencephalography - Patent 5269315 19 January 2010 18:39 UTC www.freepatentsonline.com [Source type: Academic]

.Currents that are tangential to the scalp are not picked up by the EEG. The EEG therefore benefits from the parallel, radial arrangement of apical dendrites in the cortex.^ An EEG is made by placing electrodes (small terminals which conduct an electrical current) on the subject's scalp and connecting the electrode wires to a machine known as an electroencephalograph.
  • Electroencephalogram (EEG) - Making an encephalogram, Beam enhances the value of the eeg 12 September 2009 8:15 UTC www.discoveriesinmedicine.com [Source type: Academic]

^ It is not possible to determine the activity within a single dendrite or neuron from the scalp EEG. Rather, surface EEG is the summation of the synchronous activity of thousands of neurons that have similar spatial orientation, radial to the scalp.
  • SFC Brain Imaging Research Centre - Electroencephalography (EEG) 19 January 2010 18:39 UTC www.sbirc.ed.ac.uk [Source type: Academic]

^ In an EEG recording, tiny voltage-fluctuations from the brain are picked up by a standard array of metal disks attached to the scalp and are then amplified electronically in order to create a permanent recording.
  • Electroencephalograms (EEGs): Catching a Brain Wave 1 October 2009 5:29 UTC www.cordingleyneurology.com [Source type: FILTERED WITH BAYES]

.Because voltage fields fall off with the fourth power of the radius, activity from deep sources is more difficult to detect than currents near the skull[7].^ Quantitative EEG techniques represent an advance over traditional EEG methods because they permit the detection of trends which are difficult or impossible to discern by direct visual inspection of the EEG voltage tracings.
  • Determining the nature of brain lesions by electroencephalography - Patent 5269315 19 January 2010 18:39 UTC www.freepatentsonline.com [Source type: Academic]
  • Diagnosing brain conditions by quantitative electroencephalography - Patent 5230346 19 January 2010 18:39 UTC www.freepatentsonline.com [Source type: Academic]

^ Spectral ratios showed more consistent differences between demented and non-demented subjects than did power measures.
  • Diagnosing brain conditions by quantitative electroencephalography - Patent 5230346 19 January 2010 18:39 UTC www.freepatentsonline.com [Source type: Academic]

^ Frequency-specific sources of the auditory N19-P30 detected by a multiple source analysis of evoked magnetic fields and potentials.
  • Prepulse Effects as a Function of Cortical Projection System 19 January 2010 18:39 UTC rsimons.psych.udel.edu [Source type: Academic]

.Scalp EEG activity shows oscillations at a variety of frequencies.^ Averaging was indispensable to show the event-related activity, which is normally invisible in the on-going EEG background.
  • BioMedical Engineering OnLine | Full text | On the methodological unification in electroencephalography 19 January 2010 18:39 UTC www.biomedical-engineering-online.com [Source type: Academic]

^ Somatic evoked high-frequency magnetic oscillations reflect activity of inhibitory interneurons in the human somatosensory cortex.
  • I-LABS: Toshiaki Imada, Ph.D. - Publications 19 January 2010 18:39 UTC ilabs.washington.edu [Source type: Academic]

^ Understanding the EEG requires understanding the sources of the electrical activity in the cortex and the reasons for the constant, rhythmical oscillations in polarity and amplitude.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

.Several of these oscillations have characteristic frequency ranges, spatial distributions and are associated with different states of brain functioning (e.g., waking and the various sleep stages).^ A method as claimed in claim 40 wherein the value facilitates distinguishing between conditions with different functional connections related to brain dysfunction of the underlying tracts.
  • Diagnosing brain conditions by quantitative electroencephalography - Patent 5230346 19 January 2010 18:39 UTC www.freepatentsonline.com [Source type: Academic]

^ In these diseases, gradual severing of the connections that link different brain areas eventually may cause the symptoms of mental and neurological disability.
  • Determining the nature of brain lesions by electroencephalography - Patent 5269315 19 January 2010 18:39 UTC www.freepatentsonline.com [Source type: Academic]

^ These bursts, which are symmetrically distributed with highest amplitude on the midline, are frequently associated with eye movements which occur 1-3 sec after the EEG event.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

.These oscillations represent synchronized activity over a network of neurons.^ These oscillations are produced by large masses of neurons (typically 10 4 – 10 7 [ 24 ]).
  • BioMedical Engineering OnLine | Full text | On the methodological unification in electroencephalography 19 January 2010 18:39 UTC www.biomedical-engineering-online.com [Source type: Academic]

^ Synchronization and desynchronization of these neural masses cannot be instantaneous, so the oscillations exhibit some waxing and waning.
  • BioMedical Engineering OnLine | Full text | On the methodological unification in electroencephalography 19 January 2010 18:39 UTC www.biomedical-engineering-online.com [Source type: Academic]

^ Pacemaker neurons distributed throughout the thalamus normally oscillate synchronously in the 7.5–12.5-Hz frequency range.
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

.The neuronal networks underlying some of these oscillations are understood (e.g., the thalamocortical resonance underlying sleep spindles), while many others are not (e.g., the system that generates the posterior basic rhythm).^ It is also reasonable to expect sensitivity in these measures to many dysfunctions believed to be abnormal in some psychiatric disorders.
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

^ However, further research into the subjective experiences which accompany alpha biofeedback training reveal that there are many other factors involved which influence these experiences.
  • Binaural Beat Stimulation Combined with Alpha Biofeedback 19 January 2010 18:39 UTC web-us.com [Source type: Academic]

^ Transient EEG structures – sleep spindles, K-complexes, epileptic spikes and many others – are obviously undetectable from the spectral estimates.
  • BioMedical Engineering OnLine | Full text | On the methodological unification in electroencephalography 19 January 2010 18:39 UTC www.biomedical-engineering-online.com [Source type: Academic]

.Research that measures both EEG and neuron spiking finds the relationship between the two is complex with the power of surface EEG only in two bands that of gamma and delta relating to neuron spike activity.^ Relationship between EEG and behavior.
  • Binaural Beat Stimulation Combined with Alpha Biofeedback 19 January 2010 18:39 UTC web-us.com [Source type: Academic]
  • Neurotainment video game systems and mind contolled machines are closer than you think. 19 January 2010 18:39 UTC www.neurovector.com [Source type: Academic]

^ Cox proportional hazards models, with adjustment for age and sex were used to estimate relationships between EEG measures and survival.
  • Arch Neurol -- Quantitative Spectral Electroencephalography in Predicting Survival in Patients With Early Alzheimer Disease, August 1998, Claus et al. 55 (8): 1105 19 January 2010 18:39 UTC archneur.ama-assn.org [Source type: Academic]

^ The examination of the cordance map distribution of the absolute power and relative power in the delta and theta bands particularly over the surface of the brain provides useful information.
  • Determining the nature of brain lesions by electroencephalography - Patent 5269315 19 January 2010 18:39 UTC www.freepatentsonline.com [Source type: Academic]

[8]

Clinical use

.A routine clinical EEG recording typically lasts 20–30 minutes (plus preparation time) and usually involves recording from 25 scalp electrodes.^ Clinical EEG, Vol 30 No.
  • Curriculum Vitae 19 January 2010 18:39 UTC www.neuro-doc.com [Source type: Academic]

^ To record the EEG, small needle electrodes (e.g.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ Clinical EEG, Vol.30 No.
  • Curriculum Vitae 19 January 2010 18:39 UTC www.neuro-doc.com [Source type: Academic]

Routine EEG is typically used in the following clinical circumstances:
.At times, a routine EEG is not sufficient, particularly when it is necessary to record a patient while he/she is having a seizure.^ The EEG is a record of the spontaneous electrical activity of the cerebral cortex; no stimulation is necessary to record it.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ By stacking up graphs of successive periods, it provides a concise, visual record of the EEG frequency changes over time ( Figure 4 ).
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ Some EEG abnormalities, for example focal spikes, can be recorded from patients during general anesthesia; 5,18 however, some general anesthetics induce spikes and thus can confuse interpretation.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

.In this case, the patient may be admitted to the hospital for days or even weeks, while EEG is constantly being recorded (along with time-synchronized video and audio recording).^ Only the cerebral cortex is represented in the EEG, other parts of the brain may influence it indirectly but do not contribute to the voltages recorded.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ Patients with eating disorders frequently give a history of physical or sexual abuse as children, so the increase in EEG abnormalities in this group may be related to their abuse history.
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

^ Durka P, Żygierewicz J, Klekowicz H, Ginter J, Blinowska K: On the statistical significance of event-related EEG desynchronization and synchronization in the time-frequency plane.
  • BioMedical Engineering OnLine | Full text | On the methodological unification in electroencephalography 19 January 2010 18:39 UTC www.biomedical-engineering-online.com [Source type: Academic]

.A recording of an actual seizure (i.e., an ictal recording, rather than an inter-ictal recording of a possibly epileptic patient at some period between seizures) can give significantly better information about whether or not a spell is an epileptic seizure and the focus in the brain from which the seizure activity emanates.^ Therefore, regional measures of power and spectral ratios have been used, while measures of activity shared between brain regions (i.e., coherence) largely have been ignored.
  • Diagnosing brain conditions by quantitative electroencephalography - Patent 5230346 19 January 2010 18:39 UTC www.freepatentsonline.com [Source type: Academic]

^ In anorexia nervosa, abnormal background activity in the EEG can be seen in nearly 60% of patients, possibly related to the effect of starvation on cerebral metabolism.
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

^ Such information might aid in development of prophylactic rather than remedial pharmacotherapeutic interventions, intended to prevent or slow further progress of the illness.
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

Epilepsy monitoring is typically done:
Additionally, EEG may be used to monitor certain procedures:
EEG can also be used in intensive care units for brain function monitoring:
  • to monitor for non-convulsive seizures/non-convulsive status epilepticus
  • to monitor the effect of sedative/anesthesia in patients in medically induced coma (for treatment of refractory seizures or increased intracranial pressure)
  • to monitor for secondary brain damage in conditions such as subarachnoid hemorrhage (currently a research method)
.If a patient with epilepsy is being considered for resective surgery, it is often necessary to localize the focus (source) of the epileptic brain activity with a resolution greater than what is provided by scalp EEG. This is because the cerebrospinal fluid, skull and scalp smear the electrical potentials recorded by scalp EEG. In these cases, neurosurgeons typically implant strips and grids of electrodes (or penetrating depth electrodes) under the dura mater, through either a craniotomy or a burr hole.^ Behavior and brain electrical activity.
  • James D. Frost, Jr., M.D. - Neurology Faculty - Baylor College of Medicine, Houston, Texas 19 January 2010 18:39 UTC www.bcm.edu [Source type: Academic]

^ The recording electrodes are positioned on the scalp and their integrated output displays the rhythmic activity of the brain.

^ The collective electrical activity of a specific region in the brain is known as the local field potential.

.The recording of these signals is referred to as electrocorticography (ECoG), subdural EEG (sdEEG) or intracranial EEG (icEEG)--all terms for the same thing.^ Rhythmic activity has been recognized as a prominent feature of the signal since the beginnings of EEG recordings.
  • BioMedical Engineering OnLine | Full text | On the methodological unification in electroencephalography 19 January 2010 18:39 UTC www.biomedical-engineering-online.com [Source type: Academic]

^ These techniques, combined with visual analysis of recorded EEG traces, constitute the canon of contemporary clinical electroencephalography.
  • BioMedical Engineering OnLine | Full text | On the methodological unification in electroencephalography 19 January 2010 18:39 UTC www.biomedical-engineering-online.com [Source type: Academic]

^ The analog signal provides a conventional EEG waveform record as indicated.
  • Determining the nature of brain lesions by electroencephalography - Patent 5269315 19 January 2010 18:39 UTC www.freepatentsonline.com [Source type: Academic]

.The signal recorded from ECoG is on a different scale of activity than the brain activity recorded from scalp EEG. Low voltage, high frequency components that cannot be seen easily (or at all) in scalp EEG can be seen clearly in ECoG. Further, smaller electrodes (which cover a smaller parcel of brain surface) allow even lower voltage, faster components of brain activity to be seen.^ Magnetoencephalography: Recording brain activities.
  • I-LABS: Toshiaki Imada, Ph.D. - Publications 19 January 2010 18:39 UTC ilabs.washington.edu [Source type: Academic]

^ To record the EEG, small needle electrodes (e.g.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ A single electrode records a potential from an arbitrary number of such ensembles, spatially filtered by different conductivities of cortex, dura mater, skull and scalp.
  • BioMedical Engineering OnLine | Full text | On the methodological unification in electroencephalography 19 January 2010 18:39 UTC www.biomedical-engineering-online.com [Source type: Academic]

Some clinical sites record from penetrating microelectrodes.

Research use

An early EEG recording, obtained by Hans Berger in 1924. The upper tracing is EEG, and the lower is a 10 Hz timing signal.
EEG, and its derivative, ERPs, are used extensively in neuroscience, cognitive science, cognitive psychology, and psychophysiological research. .Many techniques used in research contexts are not standardized sufficiently to be used in the clinical context.^ Fann WE, Stafford JR, Malone RL, Frost JD, Jr., Richman BW. Clinical research techniques in tardive dyskinesia .
  • James D. Frost, Jr., M.D. - Neurology Faculty - Baylor College of Medicine, Houston, Texas 19 January 2010 18:39 UTC www.bcm.edu [Source type: Academic]

^ Such a high level of specificity is beyond the confidence level achieved by many routinely used clinical tests, such as mammograms, cervical screenings, or CT brain scans.
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

^ Many of the studies cited used patients categorized as early onset or mildly impaired, compatible with probable clinical utilization of these methods.
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

.A different method to study brain function is functional magnetic resonance imaging (fMRI).^ Magnetic resonance imaging (MRI) .

^ Functional magnetic resonance imaging .

^ Spence Charles The researchers in my group are studying the integration of information across the traditional sense modalities using a variety of paradigms and techniques, including human psychophysics, functional magnetic resonance imaging (fMRI), electroencephalography (EEG), and transcranial magnetic stimulation (TMS).

Some benefits of EEG compared to fMRI include:
  • Hardware costs are significantly lower for EEG sensors versus an fMRI machine
  • EEG sensors can be deployed into a wider variety of environments than can a bulky, immobile fMRI machine
  • EEG enables higher temporal resolution, on the order of milliseconds, rather than seconds
  • EEG is relatively tolerant of subject movement versus an fMRI (where the subject must remain completely still)
  • EEG is silent, which allows for better study of the responses to auditory stimuli
  • EEG does not aggravate claustrophobia
Limitations of EEG as compared with fMRI include:
  • Significantly lower spatial resolution
  • Need to apply electrodes to the scalp (which may bother people with severe tactile sensitivities, e.g., some individuals with autism)
  • ERP studies require relatively simple paradigms, compared with block-design fMRI studies
EEG recordings have been successfully obtained simultaneously with fMRI scans, though successful simultaneous recording requires that several technical issues be overcome, such as the presence of ballistocardiographic artifact, MRI pulse artifact and the induction of electrical currents in EEG wires that move within the strong magnetic fields of the MRI.
EEG also has some characteristics that compare favorably with behavioral testing:
  • EEG can detect covert processing (i.e., that which does not require a response)
  • EEG can be used in subjects who are incapable of making a motor response
  • Some ERP components can be detected even when the subject is not attending to the stimuli
  • As compared with other reaction time paradigms, ERPs can elucidate stages of processing (rather than just the final end result)

Method

Computer Electroencephalograph Neurovisor-BMM 40
.In conventional scalp EEG, the recording is obtained by placing electrodes on the scalp with a conductive gel or paste, usually after preparing the scalp area by light abrasion to reduce impedance due to dead skin cells.^ At electrode positions, the skin was prepared with alcohol to obtain impedances of less than 5 kΩ.
  • Detection of Consciousness by Electroencephalogram and Audit... : Anesthesiology 12 September 2009 8:15 UTC journals.lww.com [Source type: Academic]

^ To record the EEG, small needle electrodes (e.g.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ Thus they contrast with nerve or muscle action potentials in which small electrically active areas of axons or muscle fibers move toward, pass by and move away from the recording electrodes, e.g., when nerve conduction velocities are measured.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

.Many systems typically use electrodes, each of which is attached to an individual wire.^ An electroencephalogram (EEG) is a painless procedure that uses small, flat metal discs (electrodes) attached to your scalp to detect electrical activity in your brain.
  • EEG - MayoClinic.com 12 September 2009 8:15 UTC www.mayoclinic.com [Source type: FILTERED WITH BAYES]
  • EEG - MayoClinic.com 12 September 2009 8:15 UTC mayoclinic.com [Source type: FILTERED WITH BAYES]

^ EEG METHODS As described previously, 6 EEG recordings were performed at baseline with the use of an on-line 20-channel EEG system, with the international 10/20 system and silver–silver chloride electrodes.
  • Arch Neurol -- Quantitative Spectral Electroencephalography in Predicting Survival in Patients With Early Alzheimer Disease, August 1998, Claus et al. 55 (8): 1105 19 January 2010 18:39 UTC archneur.ama-assn.org [Source type: Academic]

^ The system most often used to place electrodes for monitoring is the International Federation 10-20 System as illustrated in Figure 4 .

.Some systems use caps or nets into which electrodes are embedded; this is particularly common when high-density arrays of electrodes are needed.^ The inferior spatial resolution of the EEG, relative to the other neuroimaging modalities, can be remedied in part through the use of high density electrode arrays and modern statistical methods of current source localization.
  • Predicting Relapse to Alcohol and Drug Abuse via Quantitative Electroencephalography 19 January 2010 18:39 UTC www.nature.com [Source type: Academic]

^ Depth electrodes, or subdural strip electrodes, are surgically implanted into the brain and are used to localize a seizure focus in preparation for epilepsy surgery.
  • Electroencephalography - procedure, test, pain, adults, time, medication, types, children, Definition, Purpose, Demographics, Description, Diagnosis/Preparation, Aftercare, Risks, Normal results, Morbidity and mortality rates 19 January 2010 18:39 UTC www.surgeryencyclopedia.com [Source type: FILTERED WITH BAYES]

^ As such, it has been common in EEG determinations to use monopolar referencing by having a linked ears reference electrode: this means by having electrodes in adjacency to each ear relatively linked.
  • Determining the nature of brain lesions by electroencephalography - Patent 5269315 19 January 2010 18:39 UTC www.freepatentsonline.com [Source type: Academic]

.Electrode locations and names are specified by the International 10–20 system[9] for most clinical and research applications (except when high-density arrays are used).^ ZipPrep electrodes (Aspect Medical Systems, Newton, MA) were applied at the left temporal region between the lateral edge of the eye and the upper edge of the ear (AT1), above the right mastoid (M2), Fpz (reference), and F7 (ground, electrode positions according to the international 10-20 system).
  • Detection of Consciousness by Electroencephalogram and Audit... : Anesthesiology 12 September 2009 8:15 UTC journals.lww.com [Source type: Academic]

^ Electrodes were applied in the standard 20 locations on the head.
  • Determining the nature of brain lesions by electroencephalography - Patent 5269315 19 January 2010 18:39 UTC www.freepatentsonline.com [Source type: Academic]

^ Biomagnetism: Fundamental research and clinical applications (pp.
  • I-LABS: Toshiaki Imada, Ph.D. - Publications 19 January 2010 18:39 UTC ilabs.washington.edu [Source type: Academic]

.This system ensures that the naming of electrodes is consistent across laboratories.^ In this recommendation, four electrodes have different names compared to the 10-20 system; these are T 7 , T 8 , P 7 , and P 8 .
  • 13. Electroencephalography 19 January 2010 18:39 UTC www.bem.fi [Source type: Academic]

^ This part of the recording should be reviewed while the patient is in the laboratory to verify the integrity of the system and the appropriate connection of electrode leads to the preamplifier.
  • Ambulatory EEG: eMedicine Clinical Procedures 19 January 2010 18:39 UTC emedicine.medscape.com [Source type: Academic]

^ Most laboratories performing routine clinical evaluations use the international 10-20 system of electrode placement.
  • Solving the inverse problem in electroencephalography 19 January 2010 18:39 UTC www.acm.org [Source type: Academic]

.In most clinical applications, 19 recording electrodes (plus ground and system reference) are used.^ If electrode S is "active", an additional recording is made using the PV electrode as reference.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ The recording is obtained by placing electrodes on the scalp, usually after preparing the scalp area by light abrasion and application of a conductive gel to reduce impedance .
  • Greatest Inventions -- Electroencephalography -- EEG 19 January 2010 18:39 UTC www.edinformatics.com [Source type: Reference]

^ The standard recording array for adults consists of 21 electrodes plus a ground electrode, as seen in figure 2.
  • Solving the inverse problem in electroencephalography 19 January 2010 18:39 UTC www.acm.org [Source type: Academic]

.A smaller number of electrodes are typically used when recording EEG from neonates.^ To record the EEG, small needle electrodes (e.g.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ A single electrode records a potential from an arbitrary number of such ensembles, spatially filtered by different conductivities of cortex, dura mater, skull and scalp.
  • BioMedical Engineering OnLine | Full text | On the methodological unification in electroencephalography 19 January 2010 18:39 UTC www.biomedical-engineering-online.com [Source type: Academic]

^ Neuroscientists and biological psychiatrists use EEGs to study the function of the brain by recording brainwaves during controlled behavior of human volunteers and animals in lab experiments.
  • Greatest Inventions -- Electroencephalography -- EEG 19 January 2010 18:39 UTC www.edinformatics.com [Source type: Reference]

.Additional electrodes can be added to the standard set-up when a clinical or research application demands increased spatial resolution for a particular area of the brain.^ Return to Main Page Also at the beginning of the Eighties, Doctor Jeffrey S. Thompson began his Brain-Mind Research project which clinically analyzed human response to sound.
  • A Visionary Sound Arts Interface 1 October 2009 5:29 UTC www.geocities.com [Source type: General]

^ By Eugene Harris   |  Published 12/21/2006 Toys Read Brain Waves in the Newest Gadgets A whole new area of toys is beginning to open up.
  • Brainwave - Associated Content - Topic - associatedcontent.com 1 October 2009 5:29 UTC www.associatedcontent.com [Source type: General]

^ Readings may be obtained for a particular brain site by coupling a single electrode with an indifferent, or neutral, lead (monopolar technique) or between two areas of the brain through two independent electrodes (bipolar technique).
  • electroencephalography Facts, information, pictures | Encyclopedia.com articles about electroencephalography 19 January 2010 18:39 UTC www.encyclopedia.com [Source type: Academic]

.High-density arrays (typically via cap or net) can contain up to 256 electrodes more-or-less evenly spaced around the scalp.^ The technician either measures the scalp and marks the spots where small discs (electrodes) will be placed or fits the head with a special cap containing between 16 and 25 of these discs.
  • Electroencephalogram - Definition, Purpose, Description, Risks, Normal results, Parental concerns, Resources 12 September 2009 8:15 UTC www.healthofchildren.com [Source type: Academic]

^ The inferior spatial resolution of the EEG, relative to the other neuroimaging modalities, can be remedied in part through the use of high density electrode arrays and modern statistical methods of current source localization.
  • Predicting Relapse to Alcohol and Drug Abuse via Quantitative Electroencephalography 19 January 2010 18:39 UTC www.nature.com [Source type: Academic]

^ In the smallest form, one or more button containing electrodes and integrated electronics can be placed on the scalp.
  • Integrated Transcranial Current Stimulation and Electroencephalography Device - Patent application 19 January 2010 18:39 UTC www.faqs.org [Source type: Academic]

.Each electrode is connected to one input of a differential amplifier (one amplifier per pair of electrodes); a common system reference electrode is connected to the other input of each differential amplifier.^ Preferred terminology now refers to one electrode as the "exploring" electrode and the other as the "reference" electrode.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ As such, it has been common in EEG determinations to use monopolar referencing by having a linked ears reference electrode: this means by having electrodes in adjacency to each ear relatively linked.
  • Determining the nature of brain lesions by electroencephalography - Patent 5269315 19 January 2010 18:39 UTC www.freepatentsonline.com [Source type: Academic]

^ A common reference electrode was placed on the right earlobe and a common ground at FPz.
  • Prepulse Effects as a Function of Cortical Projection System 19 January 2010 18:39 UTC rsimons.psych.udel.edu [Source type: Academic]

.These amplifiers amplify the voltage between the active electrode and the reference (typically 1,000–100,000 times, or 60–100 dB of voltage gain).^ Thus, the frontal and occipital power estimates are inflated, since these are the furthest points from the reference electrodes.
  • Determining the nature of brain lesions by electroencephalography - Patent 5269315 19 January 2010 18:39 UTC www.freepatentsonline.com [Source type: Academic]

^ Therefore, the reference electrode is usually placed on the head where in fact it is as active as any of the other electrodes.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ At the start of each line two electrodes are identified, with the line of tracing representing the potential difference between these electrodes.
  • Electroencephalography | Practice | Nursing Times 19 January 2010 18:39 UTC www.nursingtimes.net [Source type: FILTERED WITH BAYES]

.In analog EEG, the signal is then filtered (next paragraph), and the EEG signal is output as the deflection of pens as paper passes underneath.^ Artifact correction of ongoing EEG using spatial filters based on artifact and brain signal topographies.

^ Digital EEG recordings are extremely flexible in the way they display the EEG tracings, unlike analog paper EEG. .
  • Quantitative Electroencephalography - QEEG ("Brain Mapping") 19 January 2010 18:39 UTC learningdiscoveries.com.au [Source type: Academic]

^ Since we are only looking to detect signals up to 100Hz, this separation is more than adequate, and the isolated low-pass filter shown on the right with cutoff 160Hz cleans the signal almost completely (See signal output in results).

.Most EEG systems these days, however, are digital, and the amplified signal is digitized via an analog-to-digital converter, after being passed through an anti-aliasing filter.^ The analog signal is digitized by the A/D converter in a microcomputer to become digital data.
  • Determining the nature of brain lesions by electroencephalography - Patent 5269315 19 January 2010 18:39 UTC www.freepatentsonline.com [Source type: Academic]

^ Beckman 9852A coupler (measured time constant, 50 ms), and led through Beckman pre- and post-amplifiers (bandpass .16-150 Hz) to an analog-to-digital converter.
  • Prepulse Effects as a Function of Cortical Projection System 19 January 2010 18:39 UTC rsimons.psych.udel.edu [Source type: Academic]

^ The analog signal provides a conventional EEG waveform record as indicated.
  • Determining the nature of brain lesions by electroencephalography - Patent 5269315 19 January 2010 18:39 UTC www.freepatentsonline.com [Source type: Academic]

.Analog-to-digital sampling typically occurs at 256–512 Hz in clinical scalp EEG; sampling rates of up to 20 kHz are used in some research applications.^ Biomagnetism: Fundamental research and clinical applications (pp.
  • I-LABS: Toshiaki Imada, Ph.D. - Publications 19 January 2010 18:39 UTC ilabs.washington.edu [Source type: Academic]

^ EEG, first clinically applied in 1929 by the neuropsychiatrist Hans Berger, 258 promises to have greatly expanded use as psychiatrists become more familiar with its many applications.
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

^ Prog Neurobiol 1983; 20:185–249 [Medline] Nystrom C, Matousek M, Hallstrom T: Relationships between EEG and clinical characteristics in major depressive disorder.
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

.During the recording, a series of activation procedures may be used.^ Muscle potentials often disappear or subside during the first 3-5 minutes of the recording period if sedative drugs are used.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ Under the recording conditions used in the UCD-VMTH laboratory, drowsiness and non-REM sleep usually begin less than 10 minutes after recording begins, thus EEG observations during arousal may be rather limited.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

.These procedures may induce normal or abnormal EEG activity that might not otherwise be seen.^ Patients with eating disorders frequently give a history of physical or sexual abuse as children, so the increase in EEG abnormalities in this group may be related to their abuse history.
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

^ In the doses used, none of the drugs administered is known to elicit EEG abnormalities in normal dogs.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ In anorexia nervosa, abnormal background activity in the EEG can be seen in nearly 60% of patients, possibly related to the effect of starvation on cerebral metabolism.
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

.These procedures include hyperventilation, photic stimulation (with a strobe light), eye closure, mental activity, sleep and sleep deprivation.^ These periods of light sleep, almost devoid of alpha, affected the average alpha ratios.
  • Binaural Beat Stimulation Combined with Alpha Biofeedback 19 January 2010 18:39 UTC web-us.com [Source type: Academic]

^ Berger also noted that alpha was replaced by beta waves when the eyes were opened or when the individual was engaged in mental activity such as arithmetic calculations.
  • Binaural Beat Stimulation Combined with Alpha Biofeedback 19 January 2010 18:39 UTC web-us.com [Source type: Academic]

^ Physiological correlates of mental activity: Eye movements, alpha, and heart rate during imaging, suppression, concentration, search, and choice.
  • Binaural Beat Stimulation Combined with Alpha Biofeedback 19 January 2010 18:39 UTC web-us.com [Source type: Academic]
  • Neurotainment video game systems and mind contolled machines are closer than you think. 19 January 2010 18:39 UTC www.neurovector.com [Source type: Academic]

.During (inpatient) epilepsy monitoring, a patient's typical seizure medications may be withdrawn.^ The cordance mapping can be continually monitored during medical procedures such as surgery or in treatment in intensive care units.
  • Determining the nature of brain lesions by electroencephalography - Patent 5269315 19 January 2010 18:39 UTC www.freepatentsonline.com [Source type: Academic]

^ Hrachovy RA, Frost JD, Jr., Glaze DG. Coupling of focal electrical seizure discharges with infantile spasms: incidence during long-term monitoring in newly diagnosed patients .
  • James D. Frost, Jr., M.D. - Neurology Faculty - Baylor College of Medicine, Houston, Texas 19 January 2010 18:39 UTC www.bcm.edu [Source type: Academic]

.The digital EEG signal is stored electronically and can be filtered for display.^ Digital EEG recordings are extremely flexible in the way they display the EEG tracings, unlike analog paper EEG. .
  • Quantitative Electroencephalography - QEEG ("Brain Mapping") 19 January 2010 18:39 UTC learningdiscoveries.com.au [Source type: Academic]

^ A system according to claim 1, wherein said system includes a digital display generator means for receiving digital data stored in said recording apparatus and to generate a graphic digital display corresponding to received data.
  • Ambulatory electroencephalography system - Google Patent Search 19 January 2010 18:39 UTC www.google.com [Source type: Reference]
  • Ambulatory electroencephalography system - Google Patent Search 19 January 2010 18:39 UTC www.google.it [Source type: Reference]

^ EEG signals (in the range of milli-volts) are amplified and digitalized for later processing.
  • Surgery.com - Information on Electroencephalography Surgeons, Physicians, Specialists and Clinics. 19 January 2010 18:39 UTC www.surgery.com [Source type: Academic]

.Typical settings for the high-pass filter and a low-pass filter are 0.5-1 Hz and 35–70 Hz, respectively.^ The high-frequency cutoff was 35 Hz (-3 dB, 12 dB/octave), and the time constant was 0.3 seconds.
  • Arch Neurol -- Quantitative Spectral Electroencephalography in Predicting Survival in Patients With Early Alzheimer Disease, August 1998, Claus et al. 55 (8): 1105 19 January 2010 18:39 UTC archneur.ama-assn.org [Source type: Academic]

^ The frequency bands were set as follows: delta, 0.3 to 3.5 Hz; theta, 3.6 to 7.4 Hz; alpha, 7.5 to 12.5; and beta, 12.6 to 35.4 Hz.
  • Arch Neurol -- Quantitative Spectral Electroencephalography in Predicting Survival in Patients With Early Alzheimer Disease, August 1998, Claus et al. 55 (8): 1105 19 January 2010 18:39 UTC archneur.ama-assn.org [Source type: Academic]

.The high-pass filter typically filters out slow artifact, such as electrogalvanic signals and movement artifact, whereas the low-pass filter filters out high-frequency artifacts, such as electromyographic signals.^ Artifact correction of ongoing EEG using spatial filters based on artifact and brain signal topographies.

^ T he case for peak-to-peak measurement of P300 recorded at .3 Hz high pass filter settings in detection of deception .

^ Delta State Activities include such things as sitting silently, slow moving meditation, Automatic movement, Dance, and "Flow" in sports activities.
  • Brain waves - Psychonautics Advanced - tribe.net 16 September 2009 21:44 UTC tribes.tribe.net [Source type: Original source]

.An additional notch filter is typically used to remove artifact caused by electrical power lines (60 Hz in the United States and 50 Hz in many other countries).^ For the calculation of approximate entropy, also a 30-Hz low-pass filter was used to reduce the influence of the electromyogram.
  • Detection of Consciousness by Electroencephalogram and Audit... : Anesthesiology 12 September 2009 8:15 UTC journals.lww.com [Source type: Academic]

^ Different techniques can be used to overcome the artifacts caused by linked ear reference montage.
  • Determining the nature of brain lesions by electroencephalography - Patent 5269315 19 January 2010 18:39 UTC www.freepatentsonline.com [Source type: Academic]

^ Before averaging of electroencephalographic sweeps, a digital 25-Hz high-pass filter was applied, and for each data section of 2 s, the DC component (mean value) was removed.
  • Detection of Consciousness by Electroencephalogram and Audit... : Anesthesiology 12 September 2009 8:15 UTC journals.lww.com [Source type: Academic]

[10]
.As part of an evaluation for epilepsy surgery, it may be necessary to insert electrodes near the surface of the brain, under the surface of the dura mater.^ A single electrode records a potential from an arbitrary number of such ensembles, spatially filtered by different conductivities of cortex, dura mater, skull and scalp.
  • BioMedical Engineering OnLine | Full text | On the methodological unification in electroencephalography 19 January 2010 18:39 UTC www.biomedical-engineering-online.com [Source type: Academic]

^ Depth electrodes, or subdural strip electrodes, are surgically implanted into the brain and are used to localize a seizure focus in preparation for epilepsy surgery.
  • Electroencephalography - procedure, test, pain, adults, time, medication, types, children, Definition, Purpose, Demographics, Description, Diagnosis/Preparation, Aftercare, Risks, Normal results, Morbidity and mortality rates 19 January 2010 18:39 UTC www.surgeryencyclopedia.com [Source type: FILTERED WITH BAYES]

^ It involves the recording and evaluation of spontaneous evoked electrical activity from the brain through surface disk electrodes attached to your scalp with a conductive, adhesive cream.
  • http://www.grandriverhospital.on.ca/patient/special/pat-test-elect.cfm 19 January 2010 18:39 UTC www.grandriverhospital.on.ca [Source type: FILTERED WITH BAYES]

This is accomplished via burr hole or craniotomy. .This is referred to variously as "electrocorticography (ECoG)", "intracranial EEG (I-EEG)" or "subdural EEG (SD-EEG)". Depth electrodes may also be placed into brain structures, such as the amygdala or hippocampus, structures which are common epileptic foci and may not be "seen" clearly by scalp EEG. The electrocorticographic signal is processed in the same manner as digital scalp EEG (above), with a couple of caveats.^ A common reference electrode was placed on the right earlobe and a common ground at FPz.
  • Prepulse Effects as a Function of Cortical Projection System 19 January 2010 18:39 UTC rsimons.psych.udel.edu [Source type: Academic]

^ Only the cerebral cortex is represented in the EEG, other parts of the brain may influence it indirectly but do not contribute to the voltages recorded.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ As such, it has been common in EEG determinations to use monopolar referencing by having a linked ears reference electrode: this means by having electrodes in adjacency to each ear relatively linked.
  • Determining the nature of brain lesions by electroencephalography - Patent 5269315 19 January 2010 18:39 UTC www.freepatentsonline.com [Source type: Academic]

.ECoG is typically recorded at higher sampling rates than scalp EEG because of the requirements of Nyquist theorem—the subdural signal is composed of a higher predominance of higher frequency components.^ The BGR consist of predominant 6-8 or 6-10 Hz waves of 10-20 FV amplitude, with superimposed random slower and higher frequencies ( Figure 12 ).
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ BGR during full arousal are usually of very low amplitude ( < 20 mV), with higher frequencies (15-25 Hz) predominating ( Figure 11 ).
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ Some EEG amplifiers have a much higher high-frequency limit but this is not used effectively, since the highest frequencies that can be recorded are limited to about 75-90 Hz by the inertia of the pens and pen drivers.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

.Also, many of the artifacts which affect scalp EEG do not impact ECoG, and therefore display filtering is often not needed.^ Artifact correction of ongoing EEG using spatial filters based on artifact and brain signal topographies.

^ The basis of many brain wave-reading games is electroencephalography, or EEG, the measurement of the brain's electrical activity through electrodes placed on the scalp.
  • New toys read brain waves 16 September 2009 21:44 UTC www.cbc.ca [Source type: News]

^ Eye movements often are accompanied by eyelid movements (e.g., blinking) and/or with movements of the scalp, either of which may be associated with muscle potentials and/or electrode/wire movement artifacts.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

.A typical adult human EEG signal is about 10µV to 100 µV in amplitude when measured from the scalp [11] and is about 10–20 mV when measured from subdural electrodes.^ A method as claimed in claim 23 wherein the energy measured by the electrodes for each channel is obtained with reference to multiple electrodes about the head.
  • Determining the nature of brain lesions by electroencephalography - Patent 5269315 19 January 2010 18:39 UTC www.freepatentsonline.com [Source type: Academic]

^ A method as claimed in claim 19 wherein the first data are obtained from energy measured by selected electrode channels, and locating the selected electrode channels strategically about the brain.
  • Determining the nature of brain lesions by electroencephalography - Patent 5269315 19 January 2010 18:39 UTC www.freepatentsonline.com [Source type: Academic]

^ EEG METHODS As described previously, 6 EEG recordings were performed at baseline with the use of an on-line 20-channel EEG system, with the international 10/20 system and silver–silver chloride electrodes.
  • Arch Neurol -- Quantitative Spectral Electroencephalography in Predicting Survival in Patients With Early Alzheimer Disease, August 1998, Claus et al. 55 (8): 1105 19 January 2010 18:39 UTC archneur.ama-assn.org [Source type: Academic]

.Since an EEG voltage signal represents a difference between the voltages at two electrodes, the display of the EEG for the reading encephalographer may be set up in one of several ways.^ This signal consists of the difference in the voltage between the pair.
  • electroencephalography (medicine) -- Britannica Online Encyclopedia 19 January 2010 18:39 UTC www.britannica.com [Source type: Academic]

^ Readings from electrodes of an EEG unit have been taken.
  • Determining the nature of brain lesions by electroencephalography - Patent 5269315 19 January 2010 18:39 UTC www.freepatentsonline.com [Source type: Academic]

^ With regards to the diagnosis and treatment of epilepsy, Electroencephalography or EEG involves connecting the head to various electrodes to a machine that would monitor activity between different points on the surface of the brain.
  • What is an "Electroencephalography" or "EEG"? Epilepsy Diagnosis And Treatment (Health & Wellbeing: Epilepsy) 19 January 2010 18:39 UTC www.videojug.com [Source type: FILTERED WITH BAYES]

The representation of the EEG channels is referred to as a montage.
Bipolar montage 
Each channel (i.e., waveform) represents the difference between two adjacent electrodes. The entire montage consists of a series of these channels. For example, the channel "Fp1-F3" represents the difference in voltage between the Fp1 electrode and the F3 electrode. The next channel in the montage, "F3-C3," represents the voltage difference between F3 and C3, and so on through the entire array of electrodes.
Referential montage
Each channel represents the difference between a certain electrode and a designated reference electrode. There is no standard position at which this reference is always placed; it is, however, at a different position than the "recording" electrodes. Midline positions are often used because they do not amplify the signal in one hemisphere vs. the other. Another popular reference is "linked ears," which is a physical or mathematical average of electrodes attached to both earlobes or mastoids.
Average reference montage 
The outputs of all of the amplifiers are summed and averaged, and this averaged signal is used as the common reference for each channel.
Laplacian montage 
Each channel represents the difference between an electrode and a weighted average of the surrounding electrodes.[12]
.When analog (paper) EEGs are used, the technologist switches between montages during the recording in order to highlight or better characterize certain features of the EEG. With digital EEG, all signals are typically digitized and stored in a particular (usually referential) montage; since any montage can be constructed mathematically from any other, the EEG can be viewed by the electroencephalographer in any display montage that is desired.^ Digital EEG recordings are extremely flexible in the way they display the EEG tracings, unlike analog paper EEG. .
  • Quantitative Electroencephalography - QEEG ("Brain Mapping") 19 January 2010 18:39 UTC learningdiscoveries.com.au [Source type: Academic]

^ Rhythmic activity has been recognized as a prominent feature of the signal since the beginnings of EEG recordings.
  • BioMedical Engineering OnLine | Full text | On the methodological unification in electroencephalography 19 January 2010 18:39 UTC www.biomedical-engineering-online.com [Source type: Academic]

^ A: Code 95957 should not be used simply when the EEG was recorded digitally.
  • Coding FAQs -- American Academy of Neurology 19 January 2010 18:39 UTC www.aan.com [Source type: FILTERED WITH BAYES]

.The EEG is read by a neurologist, optimally one who has specific training in the interpretation of EEGs.^ Open interviews revealed that one subject who was certain he had found the key and was controlling his alpha was in actuality producing no more EEG alpha than before.
  • Binaural Beat Stimulation Combined with Alpha Biofeedback 19 January 2010 18:39 UTC web-us.com [Source type: Academic]

This is done by visual inspection of the waveforms. .The use of computer signal processing of the EEG—so-called quantitative EEG—is somewhat controversial when used for clinical purposes (although there are many research uses).^ However, further research into the subjective experiences which accompany alpha biofeedback training reveal that there are many other factors involved which influence these experiences.
  • Binaural Beat Stimulation Combined with Alpha Biofeedback 19 January 2010 18:39 UTC web-us.com [Source type: Academic]

^ EEG, first clinically applied in 1929 by the neuropsychiatrist Hans Berger, 258 promises to have greatly expanded use as psychiatrists become more familiar with its many applications.
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

^ Such a high level of specificity is beyond the confidence level achieved by many routinely used clinical tests, such as mammograms, cervical screenings, or CT brain scans.
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

Limitations

.EEG has several limitations.^ In most veterinary EEG laboratories the number of amplifiers is limited, therefore it is helpful to devise several montages so that recordings can be made from the entire dorsolateral area of each cortex.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

.Most important is its poor spatial resolution.^ Scalp electrodes are able to measure this value with poor spatial resolution.

.EEG is most sensitive to a particular set of post-synaptic potentials: those which are generated in superficial layers of the cortex, on the crests of gyri directly abutting the skull and radial to the skull.^ A single electrode records a potential from an arbitrary number of such ensembles, spatially filtered by different conductivities of cortex, dura mater, skull and scalp.
  • BioMedical Engineering OnLine | Full text | On the methodological unification in electroencephalography 19 January 2010 18:39 UTC www.biomedical-engineering-online.com [Source type: Academic]

^ Studies correlating surface events and intracellular events in cortical neurons show a direct relationship of post-synaptic potentials (PSPs) and surface potentials.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ Studies in the cat indicate that potentials originating on the surfaces of the gyri oriented parallel to the skull have maximal effects on surface electrodes, whereas those arising in the depths of the convolutions have minimal effects.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

.Dendrites which are deeper in the cortex, inside sulci, in midline or deep structures (such as the cingulate gyrus or hippocampus), or producing currents which are tangential to the skull, have far less contribution to the EEG signal.^ Only the cerebral cortex is represented in the EEG, other parts of the brain may influence it indirectly but do not contribute to the voltages recorded.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ The glial cell contribution to the EEG results from potential changes in cortical neurons which cause transient changes in extracellular K+ ; these in turn produce passive depolarizations in membrane potentials of glial cells.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ In this example as illustrated, the EEG unit employed was a system known as QSI 9000 produced by Quantified Signal Imaging, Inc.
  • Determining the nature of brain lesions by electroencephalography - Patent 5269315 19 January 2010 18:39 UTC www.freepatentsonline.com [Source type: Academic]

.The meninges, cerebrospinal fluid and skull "smear" the EEG signal, obscuring its intracranial source.^ In one embodiment of the invention, brain activity is revealed by the EEG signal, as measured with multiple electrodes on the surface of the skull.
  • Method and device for producing a desired brain state - Patent 6488617 12 September 2009 8:15 UTC www.freepatentsonline.com [Source type: Reference]

^ A set of electrodes 1 is placed in strategic positions on the surface of the skull as a means for measuring the EEG signal of an individual.
  • Method and device for producing a desired brain state - Patent 6488617 12 September 2009 8:15 UTC www.freepatentsonline.com [Source type: Reference]

^ For purposes of the present invention, any structure which holds the electrodes tightly against the skull and does not interfere with the EEG signal can be used.
  • Method and device for producing a desired brain state - Patent 6488617 12 September 2009 8:15 UTC www.freepatentsonline.com [Source type: Reference]

.It is mathematically impossible to reconstruct a unique intracranial current source for a given EEG signal[citation needed], as some currents produce potentials that cancel each other out.^ Considerable attention is currently being given to the correlation of EEG or QEEG brain mapping with other brain functional mapping methods such as PET, SPECT, and MRI. Methods have been developed for the estimation of three-dimensional electrical source distributions in the brain computed from scalp recordings.
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

^ In this example as illustrated, the EEG unit employed was a system known as QSI 9000 produced by Quantified Signal Imaging, Inc.
  • Determining the nature of brain lesions by electroencephalography - Patent 5269315 19 January 2010 18:39 UTC www.freepatentsonline.com [Source type: Academic]

This is referred to as the inverse problem. .However, much work has been done to produce remarkably good estimates of, at least, a localized electric dipole that represents the recorded currents.^ Electroencephalogr Clin Neurophysiol 1992; 82:112–118 [Medline] Buckner H, Knoll G, Fuchs M, et al: Inverse localization of electric dipole current sources in finite element models of the human head.
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

EEG vs fMRI and PET

.EEG has several strong points as a tool for exploring brain activity.^ Information which is obtainable from an EEG includes conventional EEG data representative of electrical activity in different brain regions.
  • Determining the nature of brain lesions by electroencephalography - Patent 5269315 19 January 2010 18:39 UTC www.freepatentsonline.com [Source type: Academic]

^ When this data is digitized and processed as in quantitative EEG ("qEEG"), it is possible to obtain topographical brain mapping of electrical activity in different brain regions.
  • Determining the nature of brain lesions by electroencephalography - Patent 5269315 19 January 2010 18:39 UTC www.freepatentsonline.com [Source type: Academic]

^ Conclusion: Both EEG and QEEG studies report that a high proportion of patients with mood disorders display abnormal brain electrical activity.
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

.EEG's can detect changes within a millisecond timeframe, excellent considering an action potential takes approximately 0.5-130 milliseconds to propagate across a single neuron, depending on the type of neuron[13].^ Frost JD, Jr. An averaging technique for detection of EEG-intracellular potential relationships .
  • James D. Frost, Jr., M.D. - Neurology Faculty - Baylor College of Medicine, Houston, Texas 19 January 2010 18:39 UTC www.bcm.edu [Source type: Academic]

^ Frost JD, Jr. Statistical analysis of EEG-single neuron relationships .
  • James D. Frost, Jr., M.D. - Neurology Faculty - Baylor College of Medicine, Houston, Texas 19 January 2010 18:39 UTC www.bcm.edu [Source type: Academic]

^ Thus, the potentials recorded at the surface are the algebraic sum of somewhat synchronous contributions by neuronal synapses, which change rapidly and in either direction, positive or negative, and glial cells, which operate slowly and show only depolarization, producing a smoothing, integrating effect on the EEG. 13 .
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

.Other methods of looking at brain activity, such as PET and fMRI have time resolution between seconds and minutes.^ By this invention, there is provided a method, apparatus, and system for obtaining useful assessment and diagnosis of the brain based upon electrical activity.
  • Determining the nature of brain lesions by electroencephalography - Patent 5269315 19 January 2010 18:39 UTC www.freepatentsonline.com [Source type: Academic]

^ New three-dimensional QEEG imaging methods offer an economical alternative to other functional brain imaging modalities.
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

^ Considerable attention is currently being given to the correlation of EEG or QEEG brain mapping with other brain functional mapping methods such as PET, SPECT, and MRI. Methods have been developed for the estimation of three-dimensional electrical source distributions in the brain computed from scalp recordings.
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

.EEG measures the brain's electrical activity directly, while other methods record changes in blood flow (e.g., SPECT, fMRI) or metabolic activity (e.g., PET), which are indirect markers of brain electrical activity.^ SPECT scanning measures cerebral blood flow, which is an indirect measure of metabolism and therefore brain function.
  • Determining the nature of brain lesions by electroencephalography - Patent 5269315 19 January 2010 18:39 UTC www.freepatentsonline.com [Source type: Academic]

^ In an EEG, this faint electrical activity is measured by putting electrodes on the scalp.
  • EEG - Shands Healthcare 19 January 2010 18:39 UTC www.shands.org [Source type: FILTERED WITH BAYES]

^ Behavior and brain electrical activity.
  • James D. Frost, Jr., M.D. - Neurology Faculty - Baylor College of Medicine, Houston, Texas 19 January 2010 18:39 UTC www.bcm.edu [Source type: Academic]

.EEG can be used simultaneously with fMRI so that high-temporal-resolution data can be recorded at the same time as high-spatial-resolution data, however, since the data derived from each occurs over a different time course, the data sets do not necessarily represent the exact same brain activity.^ The EEG can be used to localize the region of the brain where the abnormal electrical activity is occurring.
  • Electroencephalography - procedure, test, pain, adults, time, medication, types, children, Definition, Purpose, Demographics, Description, Diagnosis/Preparation, Aftercare, Risks, Normal results, Morbidity and mortality rates 19 January 2010 18:39 UTC www.surgeryencyclopedia.com [Source type: FILTERED WITH BAYES]

^ Electroencephalogram (EEG) - A procedure that uses electrodes on the scalp to record electrical activity of the brain.
  • Brain Injury Glossary E 12 September 2009 8:15 UTC www.waiting.com [Source type: FILTERED WITH BAYES]

^ Information which is obtainable from an EEG includes conventional EEG data representative of electrical activity in different brain regions.
  • Determining the nature of brain lesions by electroencephalography - Patent 5269315 19 January 2010 18:39 UTC www.freepatentsonline.com [Source type: Academic]
  • Diagnosing brain conditions by quantitative electroencephalography - Patent 5230346 19 January 2010 18:39 UTC www.freepatentsonline.com [Source type: Academic]

There are technical difficulties associated with combining these two modalities, including the need to remove the MRI gradient artifact present during MRI acquisition and the ballistocardiographic artifact (resulting from the pulsatile motion of blood and tissue) from the EEG. Furthermore, currents can be induced in moving EEG electrode wires due to the magnetic field of the MRI.
.EEG can be recorded at the same time as MEG so that data from these complementary high-time-resolution techniques can be combined.^ Surprisingly, the amplitude of eye-movement artifacts in the EEG channels can be rather high, sometimes exceeding the amplitude recorded by the EOG electrodes ( Figure 5, 6 ).
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ Brain Topogr 1992; 5:103–111 [Medline] Gevins A, Le J, Martin NK, et al: High resolution EEG:124 channel recording, spatial deblurring and MRI integration methods.
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

^ By stacking up graphs of successive periods, it provides a concise, visual record of the EEG frequency changes over time ( Figure 4 ).
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

Normal activity

One second of EEG signal
.The EEG is typically described in terms of (1) rhythmic activity and (2) transients.^ Here, we review the physiological basis of the EEG, and describe technique, equipment, artifacts, normal background rhythms and normal transient events in awake and sleeping dogs.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ Understanding the EEG requires understanding the sources of the electrical activity in the cortex and the reasons for the constant, rhythmical oscillations in polarity and amplitude.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ Background rhythms (BGR) are the ongoing, continuous EEG activity which forms the setting against which transient events occur.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

.The rhythmic activity is divided into bands by frequency.^ Neurophysiological Basis of EEG Research on the origins of rhythmic brain electrical activity in the various frequency bands indicates that anatomically complex homeostatic systems regulate the EEG power spectrum.
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

^ Since absolute values may suffer from large variability, relative values (percentage) were calculated by dividing the absolute power in each frequency band by the total power of the whole spectrum in all 4 bands.
  • Arch Neurol -- Quantitative Spectral Electroencephalography in Predicting Survival in Patients With Early Alzheimer Disease, August 1998, Claus et al. 55 (8): 1105 19 January 2010 18:39 UTC archneur.ama-assn.org [Source type: Academic]

^ The absolute power values are processed by computer means into relative power values by dividing, for each channel, the amount of power present in a given frequency band by the total power for each channel.
  • Determining the nature of brain lesions by electroencephalography - Patent 5269315 19 January 2010 18:39 UTC www.freepatentsonline.com [Source type: Academic]

.To some degree, these frequency bands are a matter of nomenclature (i.e., any rhythmic activity between 8–12 Hz can be described as "alpha"), but these designations arose because rhythmic activity within a certain frequency range was noted to have a certain distribution over the scalp or a certain biological significance.^ Although the alpha range is usually defined to be from 8-12 Hz, within this range the actual dominant alpha frequency varies between individuals (Schwibbe, Bruell, & Becker, 1981), within individuals across time according to differing conditions (Banquet, 1972, 1973), and within some individuals' brains at the same time (Inouye, Shinosaki, Yagasaki, & Shimizu, 1986).
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^ In addition, it contained 4 parameters that were calculated from the electroencephalogram: approximate entropy, kurtosis, skewness, and the median frequency of the frequency range 8-30 Hz.
  • Detection of Consciousness by Electroencephalogram and Audit... : Anesthesiology 12 September 2009 8:15 UTC journals.lww.com [Source type: Academic]

^ The BGR consist of predominant 6-8 or 6-10 Hz waves of 10-20 FV amplitude, with superimposed random slower and higher frequencies ( Figure 12 ).
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

.Frequency bands are usually extracted using spectral methods (for instance Welch) as implemented for instance in freely available EEG software such as EEGLAB.^ At times it is helpful to reduce the high frequency limit of the amplifiers; however, this can alter the configuration of rapid EEG events such as epileptic spikes, therefore it should be done only if absolutely necessary and only by recording for a period using the standard frequency band width.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ Artifact-free EEG evaluated relative to such norms displays few deviant values in healthy, normally functioning individuals.
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

^ Norris and Blumenthal (1996) used such a method and did demonstrate enhanced prepulse detection accuracy on trials that showed PPI compared to trials that did not.
  • Prepulse Effects as a Function of Cortical Projection System 19 January 2010 18:39 UTC rsimons.psych.udel.edu [Source type: Academic]

.Most of the cerebral signal observed in the scalp EEG falls in the range of 1–20 Hz (activity below or above this range is likely to be artifactual, under standard clinical recording techniques).^ Scalp recorded auditory evoked potentials and sonomotor responses: An evaluation of components and recording techniques.
  • Prepulse Effects as a Function of Cortical Projection System 19 January 2010 18:39 UTC rsimons.psych.udel.edu [Source type: Academic]

^ Both the electroencephalogram and AEP signals are recorded from the scalp.
  • Detection of Consciousness by Electroencephalogram and Audit... : Anesthesiology 12 September 2009 8:15 UTC journals.lww.com [Source type: Academic]

^ Since humans have an auditory range of 20 to 20,000 Hz, it is not possible to directly entrain cortical rhythms below 20 Hz with pure tones.
  • Binaural Beat Stimulation Combined with Alpha Biofeedback 19 January 2010 18:39 UTC web-us.com [Source type: Academic]

Comparison table

Comparison of EEG bands
Type Frequency (Hz) Location Normally Pathologically
Delta up to 4 frontally in adults, posteriorly in children; high amplitude waves
    .
  • adults slow wave sleep
  • in babies
  • Has been found during some continuous attention tasks (Kirmizi-Alsan et.^ Importantly, certain transient events are normal during some sleep stages and must be recognized to avoid mistaking them for PD. .
    • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

    ^ For example, increased slow activity has not been found by some workers, 136 , 137 and increased alpha 100 and decreased beta 106 , 120 have occasionally been reported.
    • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

    ^ Vertex sharp transients (V waves) are responses to stimulation, usually during drowsiness or sleep.
    • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

    al. 2006)
  • subcortical lesions
  • diffuse lesions
  • metabolic encephalopathy hydrocephalus
  • deep midline lesions
Theta 4 – 7 Hz Found in locations not related to task at hand
  • young children
  • drowsiness or arousal in older children and adults
  • idling
  • Associated with inhibition of elicited responses (has been found to spike in situations where a person is actively trying to repress a response or action) (Kirmizi-Alsan et al 2006).
  • focal subcortical lesions
  • metabolic encephalopathy
  • deep midline disorders
  • some instances of hydrocephalus
Alpha 8 – 12 Hz posterior regions of head, both sides, higher in amplitude on dominant side. Central sites (c3-c4) at rest .
  • relaxed/reflecting
  • closing the eyes
  • Also associated with inhibition control, seemingly with the purpose of timing inhibitory activity in different locations across the brain (Klimesch, Sauseng, & Hanslmayr 2007; Coan & Allen 2008).
  • coma
Beta 12 – 30 Hz both sides, symmetrical distribution, most evident frontally; low amplitude waves
  • alert/working
  • active, busy or anxious thinking, active concentration
Gamma 30 – 100 + Somatosensory cortex
  • Displays during cross-modal sensory processing (perception which combines two different senses, such as sound and sight) (Kisley & Cornwell 2006; Kanayama, Sato, & Ohira 2007; Nieuwenhuis, Yeung, & Cohen 2004)
  • Also is shown during short term memory matching of recognized objects, sounds, or tactile sensations (Herrmann, Frund, & Lenz 2009)
    .
  • A decrease in gamma band activity may be associated with cognitive decline, especially when related the theta band; however, this has not been proven for use as a clinical diagnostic measurement yet (Moretti et.^ This reduces the influence of opioid-induced activation of the δ band, which may not be related to the state of consciousness.
    • Detection of Consciousness by Electroencephalogram and Audit... : Anesthesiology 12 September 2009 8:15 UTC journals.lww.com [Source type: Academic]

    ^ Multiple studies report accurate discrimination of Alzheimer patients from depressed patients or from normal subjects by use of EEG or QEEG measures of slow activity.
    • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

    ^ However, very long events are not recorded by routine clinical methods, because capacitance-coupled ("AC") amplifiers are used.
    • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

    al. 2009).
.It should be noted that while these are the universally recognized ranges, they not concrete definitions of the range of brain-waves.^ For example, alpha-frequency brain waves may be entrained by exposing subjects to a light stimulus flickering at a rate within the alpha frequency range.
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^ Evidence from these brain imaging methods has unequivocally established that "mental illness" has definite correlates with brain dysfunction.
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

.While researchers tend to follow these guidelines, many scholars use their own specific boundaries depending on the range in which they choose to focus; additionally, some researchers define the bands using decimal values rather than rounding to whole numbers (for example, one researcher may define the lower Beta band cut-off as 12.1, while another may use the value 13), while still others sometimes divide the bands into sub-bands.^ Moreover, study populations included selected hospitalized patients 10 and small numbers of patients, 3 , 9 and the mean follow-up time was not more than 3 years.
  • Arch Neurol -- Quantitative Spectral Electroencephalography in Predicting Survival in Patients With Early Alzheimer Disease, August 1998, Claus et al. 55 (8): 1105 19 January 2010 18:39 UTC archneur.ama-assn.org [Source type: Academic]

^ Log relative percentage values of EEG bands were used as predictors.
  • Arch Neurol -- Quantitative Spectral Electroencephalography in Predicting Survival in Patients With Early Alzheimer Disease, August 1998, Claus et al. 55 (8): 1105 19 January 2010 18:39 UTC archneur.ama-assn.org [Source type: Academic]

^ Since then, numerous studies have confirmed the high specificity of normative distributions of power in the delta, theta, alpha, and beta bands.
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

Generally, this is only done for the sake of analysis.

Wave patterns

  • Delta is the frequency range up to 4 Hz.^ Pacemaker neurons distributed throughout the thalamus normally oscillate synchronously in the 7.5–12.5-Hz frequency range.
    • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

    ^ For example, alpha-frequency brain waves may be entrained by exposing subjects to a light stimulus flickering at a rate within the alpha frequency range.
    • Binaural Beat Stimulation Combined with Alpha Biofeedback 19 January 2010 18:39 UTC web-us.com [Source type: Academic]

    ^ Delta frequency waves are generally associated with deep sleep, theta waves with light sleep or dreaming, alpha waves with relaxed consciousness, and beta and gamma waves with active consciousness.
    • Binaural Beat Stimulation Combined with Alpha Biofeedback 19 January 2010 18:39 UTC web-us.com [Source type: Academic]

    .It tends to be the highest in amplitude and the slowest waves.^ V-waves can be differentiated from PD by the fact they do not have spike components, occur only during drowsiness, and are always of highest amplitude on the midline and symmetrically distributed.
    • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

    ^ Spindles, K-complexes and V waves are normal EEG transients that are of highest amplitude on the midline but are usually quite evident in electrodes located laterally, where they are symmetrical in amplitude and frequency.
    • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

    .It is seen normally in adults in slow wave sleep.^ In contrast, P50 is markedly reduced or absent at stimulation rates of 5/sec and, although unchanged during the awake and REM-sleep states, is depressed during slow-wave sleep.
    • Prepulse Effects as a Function of Cortical Projection System 19 January 2010 18:39 UTC rsimons.psych.udel.edu [Source type: Academic]

    ^ The dog's behavior and the background rhythms suggest it was in slow-wave sleep; however the focal BGR abnormality may interfere with accurate identification of the state of vigilance.
    • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

    ^ In the subacute encephalopathy associated with alcoholism, not only are slow waves noted, but epileptiform activity can also be seen, even as periodic lateralized epileptiform discharges (PLEDS).
    • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

    It is also seen normally in babies. .It may occur focally with subcortical lesions and in general distribution with diffuse lesions, metabolic encephalopathy hydrocephalus or deep midline lesions.^ Interestingly, SPECT scanning may have difficulty distinguishing between ischemia that is due to deep white-matter ischemic lesions or to infarction with cortical involvement.
    • Determining the nature of brain lesions by electroencephalography - Patent 5269315 19 January 2010 18:39 UTC www.freepatentsonline.com [Source type: Academic]

    ^ The findings further suggest that the vascular disease of MID most prominently affects broad fiber networks, that may be more vulnerable to diffuse subcortical vascular damage.
    • Diagnosing brain conditions by quantitative electroencephalography - Patent 5230346 19 January 2010 18:39 UTC www.freepatentsonline.com [Source type: Academic]

    ^ In 75% of these cases, the origin of deviant delta activity was localized near the center of the lesion volume, even in deep subcortical regions.
    • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

    .It is usually most prominent frontally in adults (e.g.^ The map in FIG. 6C is a discordance map of the same subject, showing clear and prominent frontal discordance in the theta band most prominently, and most significantly affecting the right hemisphere.
    • Determining the nature of brain lesions by electroencephalography - Patent 5269315 19 January 2010 18:39 UTC www.freepatentsonline.com [Source type: Academic]

    FIRDA - Frontal Intermittent Rhythmic Delta) and posteriorly in children (e.g. OIRDA - Occipital Intermittent Rhythmic Delta).
  • Theta is the frequency range from 4 Hz to 7 Hz.^ The BGR consist of predominant 6-8 or 6-10 Hz waves of 10-20 FV amplitude, with superimposed random slower and higher frequencies ( Figure 12 ).
    • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

    ^ Amplifiers should have maximum sensitivity in the frequency range of the EEG. A range of 0.5 to ~70 Hz is sufficient.
    • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

    ^ Pacemaker neurons distributed throughout the thalamus normally oscillate synchronously in the 7.5–12.5-Hz frequency range.
    • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

    .Theta is seen normally in young children.^ Theta waves normally are seen in sleep at any age.
    • Normal EEG Waveforms: eMedicine Neurology 19 January 2010 18:39 UTC emedicine.medscape.com [Source type: Academic]

    ^ Beta waves are normal in sleep, particularly for infants and young children.
    • Electroencephalography - procedure, test, pain, adults, time, medication, types, children, Definition, Purpose, Demographics, Description, Diagnosis/Preparation, Aftercare, Risks, Normal results, Morbidity and mortality rates 19 January 2010 18:39 UTC www.surgeryencyclopedia.com [Source type: FILTERED WITH BAYES]

    ^ These waves are normally found only when you are asleep or in young children.
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    .It may be seen in drowsiness or arousal in older children and adults; it can also be seen in meditation.^ Usually seen only during sleep in adults, the presence of theta waves in the temporal region of awake, older adults has been tentatively correlated with vascular disease.
    • Electroencephalography - procedure, test, pain, adults, time, medication, types, children, Definition, Purpose, Demographics, Description, Diagnosis/Preparation, Aftercare, Risks, Normal results, Morbidity and mortality rates 19 January 2010 18:39 UTC www.surgeryencyclopedia.com [Source type: FILTERED WITH BAYES]

    ^ CT and MRI have largely replaced echoencephalography because they produce much better images, especially in older children and adults.
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    ^ They normally are seen in deep sleep in adults as well as in infants and children.
    • Normal EEG Waveforms: eMedicine Neurology 19 January 2010 18:39 UTC emedicine.medscape.com [Source type: Academic]

    [14] .Excess theta for age represents abnormal activity.^ There may be some increase in theta activity in adults who are angry, or in those over the age of 60, but in general adults with increased theta activity are likely to have some brain disorder, such as a tumour.
    • Electroencephalography | Practice | Nursing Times 19 January 2010 18:39 UTC www.nursingtimes.net [Source type: FILTERED WITH BAYES]

    ^ ELECTROENCEPHALOGRAM (EEG) abnormalities in Alzheimer disease (AD) include increase of theta and delta activity and reduction of beta power.
    • Arch Neurol -- Quantitative Spectral Electroencephalography in Predicting Survival in Patients With Early Alzheimer Disease, August 1998, Claus et al. 55 (8): 1105 19 January 2010 18:39 UTC archneur.ama-assn.org [Source type: Academic]

    ^ Most often, the reported abnormalities have been delta and/or theta excesses in frontal areas, a decreased mean frequency and lower power in the alpha band, and increased beta power.
    • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

    .It can be seen as a focal disturbance in focal subcortical lesions; it can be seen in generalized distribution in diffuse disorder or metabolic encephalopathy or deep midline disorders or some instances of hydrocephalus.^ Some EEG abnormalities, for example focal spikes, can be recorded from patients during general anesthesia; 5,18 however, some general anesthetics induce spikes and thus can confuse interpretation.
    • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

    ^ In 75% of these cases, the origin of deviant delta activity was localized near the center of the lesion volume, even in deep subcortical regions.
    • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

    ^ Neurophysiological changes characteristically seen in the disorders reviewed in this paper may reflect disturbances of regulation in this homeostatic systemSee text for a description of this model.
    • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

    On the contrary this range has been associated with reports of relaxed, meditative, and creative states.
  • Alpha is the frequency range from 8 Hz to 12 Hz.^ The alpha-frequency binaural beats were created by presenting two pure tones, one to each ear, through a set of headphones, which differed in frequency by 10.5 Hz.
    • Binaural Beat Stimulation Combined with Alpha Biofeedback 19 January 2010 18:39 UTC web-us.com [Source type: Academic]

    ^ More specifically, the aspects of consciousness which are focused upon are those which relate to the self-regulation and management of alpha-frequency brain waves, a primary correlate of certain aspects of consciousness.
    • Binaural Beat Stimulation Combined with Alpha Biofeedback 19 January 2010 18:39 UTC web-us.com [Source type: Academic]

    ^ It was hypothesized that alpha frequency binaural beats stimulation would increase alpha brain wave production above eyes-open baseline levels.
    • Binaural Beat Stimulation Combined with Alpha Biofeedback 19 January 2010 18:39 UTC web-us.com [Source type: Academic]

    Hans Berger named the first rhythmic EEG activity he saw, the "alpha wave." This is activity in the 8–12 Hz range seen in the posterior regions of the head on both sides, being higher in amplitude on the dominant side. .It is brought out by closing the eyes and by relaxation.^ They tend to be present posteriorly more than anteriorly and are especially prominent with closed eyes and with relaxation.
    • Normal EEG Waveforms: eMedicine Neurology 19 January 2010 18:39 UTC emedicine.medscape.com [Source type: Academic]

    ^ You will be asked to lie on your back on a bed or table or relax in a chair with your eyes closed.
    • Electroencephalogram (EEG) - Yahoo! Health 12 September 2009 8:15 UTC health.yahoo.com [Source type: FILTERED WITH BAYES]
    • CIGNA - Electroencephalogram (EEG) 12 September 2009 8:15 UTC www.cigna.com [Source type: FILTERED WITH BAYES]

    ^ To protect the eyes and to prevent them from drying out, eye drops may be put into the eyes and the eye tapes may be used to close them.
    • Brain Injury Glossary E 12 September 2009 8:15 UTC www.waiting.com [Source type: FILTERED WITH BAYES]

    .It was noted to attenuate with eye opening or mental exertion.^ Alpha activity disappears normally with attention (eg, mental arithmetic, stress, opening eyes).
    • Normal EEG Waveforms: eMedicine Neurology 19 January 2010 18:39 UTC emedicine.medscape.com [Source type: Academic]

    ^ Berger also noted that alpha was replaced by beta waves when the eyes were opened or when the individual was engaged in mental activity such as arithmetic calculations.
    • Binaural Beat Stimulation Combined with Alpha Biofeedback 19 January 2010 18:39 UTC web-us.com [Source type: Academic]

    .This activity is now referred to as "posterior basic rhythm," the "posterior dominant rhythm" or the "posterior alpha rhythm."^ Electrical activity of the brain and ESP: An exploratory study of alpha rhythm and ESP scoring.
    • Binaural Beat Stimulation Combined with Alpha Biofeedback 19 January 2010 18:39 UTC web-us.com [Source type: Academic]
    • Neurotainment video game systems and mind contolled machines are closer than you think. 19 January 2010 18:39 UTC www.neurovector.com [Source type: Academic]

    ^ The control of electroencephalographic alpha rhythms through auditory feedback and the associated mental activity.
    • Binaural Beat Stimulation Combined with Alpha Biofeedback 19 January 2010 18:39 UTC web-us.com [Source type: Academic]
    • Neurotainment video game systems and mind contolled machines are closer than you think. 19 January 2010 18:39 UTC www.neurovector.com [Source type: Academic]

    ^ Efferent projections globally distributed across the cortex produce the rhythmic electrical activity known as the alpha rhythm , which dominates the EEG of an alert healthy person at rest.
    • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

    .The posterior basic rhythm is actually slower than 8 Hz in young children (therefore technically in the theta range).^ This is even more important than in the alpha and theta range.
    • brainwave mind voyages 1 October 2009 5:29 UTC mind-sync.com [Source type: FILTERED WITH BAYES]

    ^ Nucleus reticularis can hyperpolarize the cell membranes of thalamic neurons by gamma-aminobutyric acid (GABA) release, slowing the dominant alpha rhythm into the lower theta range (3.5–7.5 Hz) and diminishing sensory throughput to the cortex.
    • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

    ^ The posterior P300 can be recorded from children as young as six years, while the anterior P300 may not be present until adolescence.

    In addition to the posterior basic rhythm, there are two other normal alpha rhythms that are typically discussed: the mu rhythm and a temporal "third rhythm". Alpha can be abnormal; for example, an EEG that has diffuse alpha occurring in coma and is not responsive to external stimuli is referred to as "alpha coma".
  • Mu rhythm is alpha-range activity that is seen over the sensorimotor cortex.^ As has already been seen, the alpha rhythm is influenced by many factors, both internal and external.
    • Binaural Beat Stimulation Combined with Alpha Biofeedback 19 January 2010 18:39 UTC web-us.com [Source type: Academic]

    ^ Nucleus reticularis can hyperpolarize the cell membranes of thalamic neurons by gamma-aminobutyric acid (GABA) release, slowing the dominant alpha rhythm into the lower theta range (3.5–7.5 Hz) and diminishing sensory throughput to the cortex.
    • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

    ^ Electrical activity of the brain and ESP: An exploratory study of alpha rhythm and ESP scoring.
    • Binaural Beat Stimulation Combined with Alpha Biofeedback 19 January 2010 18:39 UTC web-us.com [Source type: Academic]

    It characteristically attenuates with movement of the contralateral arm (or mental imagery of movement of the contralateral arm).
  • Beta is the frequency range from 12 Hz to about 30 Hz.^ The BGR consist of predominant 6-8 or 6-10 Hz waves of 10-20 FV amplitude, with superimposed random slower and higher frequencies ( Figure 12 ).
    • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

    ^ Amplifiers should have maximum sensitivity in the frequency range of the EEG. A range of 0.5 to ~70 Hz is sufficient.
    • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

    ^ Pacemaker neurons distributed throughout the thalamus normally oscillate synchronously in the 7.5–12.5-Hz frequency range.
    • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

    .It is seen usually on both sides in symmetrical distribution and is most evident frontally.^ A HMPAO SPECT scan for the subject (FIG. 8A) shows globally diminished cerebral perfusion, with the most striking decreases seen in the frontal lobe (arrows).
    • Determining the nature of brain lesions by electroencephalography - Patent 5269315 19 January 2010 18:39 UTC www.freepatentsonline.com [Source type: Academic]

    ^ If you have generalised seizures (absences, primary tonic-clonic seizures, myoclonic jerks), EEG abnormality is usually seen on both sides of the brain.
    • EEG (Electroencephalogram) | Epilepsy Action 19 January 2010 18:39 UTC www.epilepsy.org.uk [Source type: General]

    ^ Subject #56 reported that he felt "a moving rolling pressure across the frontal area and then filling both sides as the beats filled my mind and the alpha increased."
    • Binaural Beat Stimulation Combined with Alpha Biofeedback 19 January 2010 18:39 UTC web-us.com [Source type: Academic]

    Beta activity is closely linked to motor behavior and is generally attenuated during active movements.[15] .Low amplitude beta with multiple and varying frequencies is often associated with active, busy or anxious thinking and active concentration.^ BGR during full arousal are usually of very low amplitude ( < 20 mV), with higher frequencies (15-25 Hz) predominating ( Figure 11 ).
    • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

    ^ EEG biofeedback of low beta band components: Frequency- specific effects on variables of attention and event-related brain potentials.

    ^ This activity appears on the screen of the EEG machine as waveforms of varying frequency and amplitude measured in voltage (specifically microvoltages).
    • Normal EEG Waveforms: eMedicine Neurology 19 January 2010 18:39 UTC emedicine.medscape.com [Source type: Academic]

    .Rhythmic beta with a dominant set of frequencies is associated with various pathologies and drug effects, especially benzodiazepines.^ The effects vary depending on the drug.
    • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

    ^ We can conclude, therefore, that the assumption of homogeneity of variance of the error effects is not violated in this data set.
    • Binaural Beat Stimulation Combined with Alpha Biofeedback 19 January 2010 18:39 UTC web-us.com [Source type: Academic]

    ^ Delta frequency waves are generally associated with deep sleep, theta waves with light sleep or dreaming, alpha waves with relaxed consciousness, and beta and gamma waves with active consciousness.
    • Binaural Beat Stimulation Combined with Alpha Biofeedback 19 January 2010 18:39 UTC web-us.com [Source type: Academic]

    .It may be absent or reduced in areas of cortical damage.^ Reduced activity in the left prefrontal cortex has been implicated in depression, and TMS may work by restoring activity in this area to normal levels.
    • Method and device for producing a desired brain state - Patent 6488617 12 September 2009 8:15 UTC www.freepatentsonline.com [Source type: Reference]

    It is the dominant rhythm in patients who are alert or anxious or who have their eyes open.
  • Gamma is the frequency range approximately 30–100 Hz.^ The BGR consist of predominant 6-8 or 6-10 Hz waves of 10-20 FV amplitude, with superimposed random slower and higher frequencies ( Figure 12 ).
    • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

    ^ Amplifiers should have maximum sensitivity in the frequency range of the EEG. A range of 0.5 to ~70 Hz is sufficient.
    • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

    ^ Pacemaker neurons distributed throughout the thalamus normally oscillate synchronously in the 7.5–12.5-Hz frequency range.
    • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

    Gamma rhythms are thought to represent binding of different populations of neurons together into a network for the purpose of carrying out a certain cognitive or motor function.
."Ultra-slow" or "near-DC" activity is recorded using DC amplifiers in some research contexts.^ Guidelines for the recording and quantitative analysis of electroencephalographic activity in research contexts.
  • ASNM - American Society of Neurophysiological Monitoring 19 January 2010 18:39 UTC www.asnm.org [Source type: Academic]

^ A paradigm of averaging coherence among multiple recording sites that overlie the distribution of known corticocortical fibers to measure the electrical activity transmitted through those fibers was used.
  • Diagnosing brain conditions by quantitative electroencephalography - Patent 5230346 19 January 2010 18:39 UTC www.freepatentsonline.com [Source type: Academic]

^ For example, increased slow activity has not been found by some workers, 136 , 137 and increased alpha 100 and decreased beta 106 , 120 have occasionally been reported.
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

.It is not typically recorded in a clinical context because the signal at these frequencies is susceptible to a number of artifacts.^ Because the AEEG is recorded outside of the controlled confines of the EEG laboratory and the patient performs customary daily activities, it is susceptible to a variety of physiological and environmental artifacts.
  • Ambulatory EEG: eMedicine Clinical Procedures 19 January 2010 18:39 UTC emedicine.medscape.com [Source type: Academic]

^ These techniques, combined with visual analysis of recorded EEG traces, constitute the canon of contemporary clinical electroencephalography.
  • BioMedical Engineering OnLine | Full text | On the methodological unification in electroencephalography 19 January 2010 18:39 UTC www.biomedical-engineering-online.com [Source type: Academic]

^ The development of portable EEG recording proved more problematic than the Holter monitor because of the need for signal amplification and multichannel recording.
  • Ambulatory EEG: eMedicine Clinical Procedures 19 January 2010 18:39 UTC emedicine.medscape.com [Source type: Academic]

.Some features of the EEG are transient rather than rhythmic.^ Rhythmic activity has been recognized as a prominent feature of the signal since the beginnings of EEG recordings.
  • BioMedical Engineering OnLine | Full text | On the methodological unification in electroencephalography 19 January 2010 18:39 UTC www.biomedical-engineering-online.com [Source type: Academic]

^ Stacks, one of the new features in Leopard, can now be viewed as a list rather than the standard grid and fan view.
  • EKU ResNet Support Blog - Gaming with Electroencephalography 19 January 2010 18:39 UTC support.resnet.eku.edu [Source type: General]

^ Some features of digital EEG make it easier and quicker to read, and other features slow it down by providing new optional tricks and tools.
  • Coding FAQs -- American Academy of Neurology 19 January 2010 18:39 UTC www.aan.com [Source type: FILTERED WITH BAYES]

.Spikes and sharp waves may represent seizure activity or interictal activity in individuals with epilepsy or a predisposition toward epilepsy.^ Berger also noted that alpha was replaced by beta waves when the eyes were opened or when the individual was engaged in mental activity such as arithmetic calculations.
  • Binaural Beat Stimulation Combined with Alpha Biofeedback 19 January 2010 18:39 UTC web-us.com [Source type: Academic]

.Other transient features are normal: vertex waves and sleep spindles are transient events which are seen in normal sleep.^ Theta waves normally are seen in sleep at any age.
  • Normal EEG Waveforms: eMedicine Neurology 19 January 2010 18:39 UTC emedicine.medscape.com [Source type: Academic]

^ Sleep spindles are repetitive sinusoidal waves.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ Theta waves are normally found during drowsiness and sleep and are normal in wakefulness in children, while delta waves are the most prominent feature of the sleeping EEG. Spikes and sharp waves are generally abnormal; however, they are common in the EEG of normal newborns.
  • Electroencephalography - procedure, test, pain, adults, time, medication, types, children, Definition, Purpose, Demographics, Description, Diagnosis/Preparation, Aftercare, Risks, Normal results, Morbidity and mortality rates 19 January 2010 18:39 UTC www.surgeryencyclopedia.com [Source type: FILTERED WITH BAYES]

.It should also be noted that there are types of activity which are statistically uncommon but are not associated with dysfunction or disease.^ Arch Neurol 1990; 47:1185–1188 Heikala EL, Laulumaa V, Soikkeli R, et al: Slow wave activity in the spectral analysis of the electroencephalogram is associated with cortical dysfunction in patients with Alzheimer's disease.
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

^ In the subacute encephalopathy associated with alcoholism, not only are slow waves noted, but epileptiform activity can also be seen, even as periodic lateralized epileptiform discharges (PLEDS).
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

.These are often referred to as "normal variants."^ Although they can occur in epileptic patients, BETS often are seen in individuals without epilepsy and can be regarded as a probable normal variant.
  • Normal EEG Waveforms: eMedicine Neurology 19 January 2010 18:39 UTC emedicine.medscape.com [Source type: Academic]

.The mu rhythm is an example of a normal variant.^ Background rhythms in normal animals vary significantly with changes in state of sleep or arousal.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

.The normal Electroencephalography (EEG) varies by age.^ Not only were the systematic changes with age confirmed, but no significant differences were found between the EEGs of normally functioning Swedish children and white or black U.S. children.
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

The neonatal EEG is quite different from the adult EEG. The EEG in childhood generally has slower frequency oscillations than the adult EEG.
.The normal EEG also varies depending on state.^ The behavioral state of the dog was judged to be that of arousal and the EEG background rhythms (BGR) are those of full arousal in a normal dog.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ Background rhythms in normal animals vary significantly with changes in state of sleep or arousal.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ For each variable, a normal range first was established from an extensive examination of data from elderly individuals in unimpaired and diseased states (FIGS. 1-6, 8, 10).
  • Diagnosing brain conditions by quantitative electroencephalography - Patent 5230346 19 January 2010 18:39 UTC www.freepatentsonline.com [Source type: Academic]

.The EEG is used along with other measurements (EOG, EMG) to define sleep stages in polysomnography.^ Filion, Dawson, and Schell (1998) have recently reviewed studies, using other perceptual measures that also provide some support for the prepulse protection-of-processing hypothesis.
  • Prepulse Effects as a Function of Cortical Projection System 19 January 2010 18:39 UTC rsimons.psych.udel.edu [Source type: Academic]

^ Multiple studies report accurate discrimination of Alzheimer patients from depressed patients or from normal subjects by use of EEG or QEEG measures of slow activity.
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

^ EMG was corrected for potential EOG contamination since these data were recorded from the same mastoid reference used for measuring ERPs, and therefore, they are subject to the same potential contaminating effects of blinks and eye movements.
  • Prepulse Effects as a Function of Cortical Projection System 19 January 2010 18:39 UTC rsimons.psych.udel.edu [Source type: Academic]

.Stage I sleep (equivalent to drowsiness in some systems) appears on the EEG as drop-out of the posterior basic rhythm.^ They consist of some form of EEG activity, which is distinct from and is superimposed on or replaces the background rhythms.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ Importantly, certain transient events are normal during some sleep stages and must be recognized to avoid mistaking them for PD. .
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ Some patients in whom epilepsy is suspected have a normal routine or sleep-deprived EEG. In these patients, AEEG can increase the chance of detecting an epileptiform abnormality.
  • Ambulatory EEG: eMedicine Clinical Procedures 19 January 2010 18:39 UTC emedicine.medscape.com [Source type: Academic]

.There can be an increase in theta frequencies.^ There is a broad consensus that increased focal or diffuse theta, decreased alpha, decreased coherence, and increased asymmetry are common EEG indicators of the postconcussion syndrome.
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

^ Most often, the reported abnormalities have been delta and/or theta excesses in frontal areas, a decreased mean frequency and lower power in the alpha band, and increased beta power.
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

.Santamaria and Chiappa cataloged a number of the variety of patterns associated with drowsiness.^ EEG of drowsiness / Joan Santamaria and Keith H. Chiappa.

.Stage II sleep is characterized by sleep spindles—transient runs of rhythmic activity in the 12–14 Hz range (sometimes referred to as the "sigma" band) that have a frontal-central maximum.^ Spindles are recorded often during non-REM sleep ( Figure 14 ).
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ Amplifiers should have maximum sensitivity in the frequency range of the EEG. A range of 0.5 to ~70 Hz is sufficient.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ Hz with lower amplitude superimposed activity, predominantly in the 6-10 Hz range.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

.Most of the activity in Stage II is in the 3–6 Hz range.^ Hz with lower amplitude superimposed activity, predominantly in the 6-10 Hz range.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ Considering that a very wide range of frequencies is conceivable, it is notable that the fluctuations are confined to a relatively narrow range, about 0.5 Hz to 50 Hz, with most well below 30 Hz.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ The LP-LF CSA shows more activity in the 5-16 Hz range than is evident in the CSA of the RP-RF derivation.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

.Stage III and IV sleep are defined by the presence of delta frequencies and are often referred to collectively as "slow-wave sleep."^ Most often, the reported abnormalities have been delta and/or theta excesses in frontal areas, a decreased mean frequency and lower power in the alpha band, and increased beta power.
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

^ In contrast, P50 is markedly reduced or absent at stimulation rates of 5/sec and, although unchanged during the awake and REM-sleep states, is depressed during slow-wave sleep.
  • Prepulse Effects as a Function of Cortical Projection System 19 January 2010 18:39 UTC rsimons.psych.udel.edu [Source type: Academic]

^ Stages of light and deep non-REM sleep are often recognizable by the higher amplitudes and lower frequencies during deep non-REM sleep.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

.Stages I-IV comprise non-REM (or "NREM") sleep.^ Non-REM Sleep .
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ Spindles are recorded often during non-REM sleep ( Figure 14 ).
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ Likewise, dogs often enter REM sleep 5 to 10 minutes after non-REM sleep begins, a briefer time than reported.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

The EEG in REM (rapid eye movement) sleep appears somewhat similar to the awake EEG.
.EEG under general anesthesia depends on the type of anesthetic employed.^ Awareness detection during caesarean section under general anaesthesia using EEG spectrum analysis.
  • ASNM - American Society of Neurophysiological Monitoring 19 January 2010 18:39 UTC www.asnm.org [Source type: Academic]

^ The EEG of dogs has been recorded clinically without premedication, 6 with sedation (tranquilization), 4, 17 and under general anesthesia.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ The present study formally tested the generality of EEG as a relapse predictor across four different types of substance dependence.
  • Predicting Relapse to Alcohol and Drug Abuse via Quantitative Electroencephalography 19 January 2010 18:39 UTC www.nature.com [Source type: Academic]

.With halogenated anesthetics, such as halothane or intravenous agents, such as propofol, a rapid (alpha or low beta), nonreactive EEG pattern is seen over most of the scalp, especially anteriorly; in some older terminology this was known as a WAR (widespread anterior rapid) pattern, contrasted with a WAIS (widespread slow) pattern associated with high doses of opiates.^ The dominant activity of the EEG power spectrum becomes more rapid, with the return of alpha activity and the higher frequency beta activity, and the flow of information through the thalamus to the cortex is facilitated.
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

^ For example, increased slow activity has not been found by some workers, 136 , 137 and increased alpha 100 and decreased beta 106 , 120 have occasionally been reported.
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

^ There is a wide consensus that delta or theta excess and alpha and beta deficits are commonly encountered in children with learning disorders and that theta or alpha excesses are often seen in children with ADD/ADHD. Alcohol and Substance Abuse The changes during acute alcoholic intoxication include the slowing of the EEG, seen in the form of decreased alpha frequency and abundance, an increased amount of theta, and even some generalized delta rhythms.
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

.Anesthetic effects on EEG signals are beginning to be understood at the level of drug actions on different kinds of synapses and the circuits that allow synchronized neuronal activity (see: http://www.stanford.edu/group/maciverlab/).^ In anorexia nervosa, abnormal background activity in the EEG can be seen in nearly 60% of patients, possibly related to the effect of starvation on cerebral metabolism.
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

^ Conceivably, as the EEG and subjective effects of binaural beats become better understood, their use as a consciousness management technique will become more effective.
  • Binaural Beat Stimulation Combined with Alpha Biofeedback 19 January 2010 18:39 UTC web-us.com [Source type: Academic]

^ Recognition of aspects of consciousness through association with EEG alpha activity represented by a light signal.
  • Binaural Beat Stimulation Combined with Alpha Biofeedback 19 January 2010 18:39 UTC web-us.com [Source type: Academic]

Artifacts

Biological artifacts

.Electrical signals detected along the scalp by an EEG, but that originate from non-cerebral origin are called artifacts.^ He is credited with the discovery of the spontaneous EEG in animals and with demonstrating the ability to detect electrical brain responses to stimuli.
  • Binaural Beat Stimulation Combined with Alpha Biofeedback 19 January 2010 18:39 UTC web-us.com [Source type: Academic]

^ The EEG is a record of the spontaneous electrical activity of the cerebral cortex; no stimulation is necessary to record it.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

.EEG data is almost always contaminated by such artifacts.^ Artifact-free EEG evaluated relative to such norms displays few deviant values in healthy, normally functioning individuals.
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

^ The data is simply a quantitative expression of the BGR; important qualitative events such as artifacts or PD can be hidden by automated analysis ( Figure 4 ).
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

The amplitude of artifacts can be quite large relative to the size of amplitude of the cortical signals of interest. .This is one of the reasons why it takes considerable experience to correctly interpret EEGs clinically.^ The equipment records the EEG from one or more channels, at intervals takes sample periods (e.g., 5 sec) from each channel, performs a frequency or interval analysis, and provides a graph of the analysis almost instantaneously.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

Some of the most common types of biological artifacts include:
  • Eye-induced artifacts (includes eye blinks and eye movements)
  • EKG (cardiac) artifacts
  • EMG (muscle activation)-induced artifacts
  • Glossokinetic artifacts
.Eye-induced artifacts are caused by the potential difference between the cornea and retina, which is quite large compared to cerebral potentials.^ Eye movements often are accompanied by eyelid movements (e.g., blinking) and/or with movements of the scalp, either of which may be associated with muscle potentials and/or electrode/wire movement artifacts.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ If two electrodes are placed on the skin over the calvaria and connected to a recording system, a constantly varying difference in potential between the electrodes is recorded.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ Eye movements cause artifacts by this means and also by a very different mechanism (below).
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

When the eye is completely still, this does not affect EEG. .But there are nearly always small or large reflexive eye movements, which generates a potential which is picked up in the frontopolar and frontal leads.^ The epochs were edited for EMG/movement (peak-to-peak deflection > 50 microvolts), lead sway and A-D converter overflow artifacts, and mathematically corrected for eye movement artifact.
  • Predicting Relapse to Alcohol and Drug Abuse via Quantitative Electroencephalography 19 January 2010 18:39 UTC www.nature.com [Source type: Academic]

^ Examination of the components before and after correction of ERPs for frontalis muscle activity suggests that contamination did occur, as evidenced by increases in negative potentials after correction of frontal leads.
  • Prepulse Effects as a Function of Cortical Projection System 19 January 2010 18:39 UTC rsimons.psych.udel.edu [Source type: Academic]

^ Mathematically there are an infinite number of initial source configurations that can generate a given scalp potential.
  • Solving the inverse problem in electroencephalography 19 January 2010 18:39 UTC www.acm.org [Source type: Academic]

.Involuntary eye movements, known as saccades, are caused by ocular muscles, which also generate electromyographic potentials.^ Generalized implementation of an eye movement correction procedure.
  • Prepulse Effects as a Function of Cortical Projection System 19 January 2010 18:39 UTC rsimons.psych.udel.edu [Source type: Academic]

.Purposeful or reflexive eye blinking also generates electromyographic potentials, but more importantly there is reflexive movement of the eyeball during blinking which gives a characteristic artifactual appearance of the EEG (see Bell's phenomenon).^ Eye movements often are accompanied by eyelid movements (e.g., blinking) and/or with movements of the scalp, either of which may be associated with muscle potentials and/or electrode/wire movement artifacts.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ Lead stimulation effects on reflex blink, exogenous brain potentials, and loudness judgments.
  • Prepulse Effects as a Function of Cortical Projection System 19 January 2010 18:39 UTC rsimons.psych.udel.edu [Source type: Academic]

^ Off-line latency and amplitude scoring of the human reflex eye blink with Fortran IV. Psychophysiology , 23 , 612 (Abstract).
  • Prepulse Effects as a Function of Cortical Projection System 19 January 2010 18:39 UTC rsimons.psych.udel.edu [Source type: Academic]

Eyelid fluttering artifacts of a characteristic type were previously called Kappa rhythm (or Kappa waves). It is usually seen in the prefrontal leads, that is, just over the eyes. Sometimes they are seen with mental activity. .They are usually in the Theta (4–7 Hz) or Alpha (8–13 Hz) range.^ The normal human EEG has a frequency range from 0.5 Hertz (Hz) to 30 Hz which is usually subdivided into four or five bands: delta (0.5-3.5 Hz), theta (4-7 Hz), alpha (8-12 Hz), beta (13-28 Hz), and gamma (28+ Hz).
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^ This is even more important than in the alpha and theta range.
  • brainwave mind voyages 1 October 2009 5:29 UTC mind-sync.com [Source type: FILTERED WITH BAYES]

^ Nucleus reticularis can hyperpolarize the cell membranes of thalamic neurons by gamma-aminobutyric acid (GABA) release, slowing the dominant alpha rhythm into the lower theta range (3.5–7.5 Hz) and diminishing sensory throughput to the cortex.
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

They were named because they were believed to originate from the brain. Later study revealed they were generated by rapid fluttering of the eyelids, sometimes so minute that it was difficult to see. .They are in fact noise in the EEG reading, and should not technically be called a rhythm or wave.^ They consist of some form of EEG activity, which is distinct from and is superimposed on or replaces the background rhythms.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ V-waves can be differentiated from PD by the fact they do not have spike components, occur only during drowsiness, and are always of highest amplitude on the midline and symmetrically distributed.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ Brain wave biofeedback research has contributed evidence of operant control of the EEG and continues to provide increasing illumination into the nature and functions of the brain's electrical rhythms.
  • Binaural Beat Stimulation Combined with Alpha Biofeedback 19 January 2010 18:39 UTC web-us.com [Source type: Academic]

Therefore, current usage in electroencephalography refers to the phenomenon as an eyelid fluttering artifact, rather than a Kappa rhythm (or wave).[16]
.Some of these artifacts are useful.^ Some of these artifacts can be confused with PD if the movements are not observed or the EOG is not recorded ( Figure 7 ).
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ Judicious use of filters, gain, and reformatting may further clarify these waveforms and assist in distinguishing seizure activity from artifact.
  • Ambulatory EEG: eMedicine Clinical Procedures 19 January 2010 18:39 UTC emedicine.medscape.com [Source type: Academic]

^ Herbert Benson in his book The Relaxation Response (1975), surveys some of the major techniques used for eliciting the relaxation response and describes the essential components of these techniques: .
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.Eye movements are very important in polysomnography, and is also useful in conventional EEG for assessing possible changes in alertness, drowsiness or sleep.^ Rapid eye movement (REM) sleep – light sleep during which brain activity is increased and the eyes move very quickly behind the eyelids.
  • arc :: Fibromyalgia 19 January 2010 18:39 UTC www.arc.org.uk [Source type: FILTERED WITH BAYES]

^ Moreover, although the data used in the scoring have been obtained from absolute power values from EEG, it is possible that other values of electrical output can be used.
  • Diagnosing brain conditions by quantitative electroencephalography - Patent 5230346 19 January 2010 18:39 UTC www.freepatentsonline.com [Source type: Academic]

^ A disadvantage of EEG mapping, however, is that it has not been possible to analyze the information obtained by the electroencephalogram to diagnose and assess effectively different conditions of the brain, and thus diseases and disorders of the brain.
  • Determining the nature of brain lesions by electroencephalography - Patent 5269315 19 January 2010 18:39 UTC www.freepatentsonline.com [Source type: Academic]

.EKG artifacts are quite common and can be mistaken for spike activity.^ Here, ECG artifact is mingled with slow waves (arrows); the result should not be mistaken for spike-wave complexes.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

.Because of this, modern EEG acquisition commonly includes a one-channel EKG from the extremities.^ Muscle artifact is common during arousal, often obscuring one or more channels of EEG ( Figure 5, 6 ).
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ The equipment records the EEG from one or more channels, at intervals takes sample periods (e.g., 5 sec) from each channel, performs a frequency or interval analysis, and provides a graph of the analysis almost instantaneously.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ Wayne Nolan's 16 and 24 channel MindSet EEG Acquisition Hardware and MindMeld EEG/qEEG acquisition and analysis software .
  • Quantitative Electroencephalography - QEEG ("Brain Mapping") 19 January 2010 18:39 UTC learningdiscoveries.com.au [Source type: Academic]

.This also allows the EEG to identify cardiac arrhythmias that are an important differential diagnosis to syncope or other episodic/attack disorders.^ Electroencephalogr Clin Neurophysiol 1994; 90:242–245 [Medline] O'Connor KP, Shaw JC, Ongley CO: The EEG and differential diagnosis in psychogeriatrics.
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

.Glossokinetic artifacts are caused by the potential difference between the base and the tip of the tongue.^ Differentiation between finger, toe and tongue movement in man based on 40-Hz EEG. Electroencephalography and clinical Neurophysiology, 90, 456-460.
  • Psycoloquy 6(06): MEMORY PROCESSES DESCRIBED AS BRAIN OSCILLATIONS 19 January 2010 18:39 UTC www.cogsci.ecs.soton.ac.uk [Source type: Academic]

^ If two electrodes are placed on the skin over the calvaria and connected to a recording system, a constantly varying difference in potential between the electrodes is recorded.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ At some fixed instant in time, a slight imbalance in sources over sinks…causes a net outward macroscopic current density…and macroscopic potential difference” (Nunez, 29).

.Minor tongue movements can contaminate the EEG, especially in parkinsonian and tremor disorders.^ Differentiation between finger, toe and tongue movement in man based on 40-Hz EEG. Electroencephalography and clinical Neurophysiology, 90, 456-460.
  • Psycoloquy 6(06): MEMORY PROCESSES DESCRIBED AS BRAIN OSCILLATIONS 19 January 2010 18:39 UTC www.cogsci.ecs.soton.ac.uk [Source type: Academic]

Environmental artifacts

In addition to artifacts generated by the body, many artifacts originate from outside the body. .Movement by the patient, or even just settling of the electrodes, may cause electrode pops, spikes originating from a momentary change in the impedance of a given electrode.^ Eye movements often are accompanied by eyelid movements (e.g., blinking) and/or with movements of the scalp, either of which may be associated with muscle potentials and/or electrode/wire movement artifacts.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ Artifacts caused by movements of the patient and by muscles in the region of the recording electrodes are a serious problem in non-sedated patients and can obscure the recording to the point where it is of little value.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ These artifacts probably arise from movements that cause the electrodes or their connecting wires to move through the ambient electromagnetic fields in the laboratory (personal observation).
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

.Poor grounding of the EEG electrodes can cause significant 50 or 60 Hz artifact, depending on the local power system's frequency.^ Surprisingly, the amplitude of eye-movement artifacts in the EEG channels can be rather high, sometimes exceeding the amplitude recorded by the EOG electrodes ( Figure 5, 6 ).
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ Neurophysiological Basis of EEG Research on the origins of rhythmic brain electrical activity in the various frequency bands indicates that anatomically complex homeostatic systems regulate the EEG power spectrum.
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

^ Artifacts caused by movements of the patient and by muscles in the region of the recording electrodes are a serious problem in non-sedated patients and can obscure the recording to the point where it is of little value.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

.A third source of possible interference can be the presence of an IV drip; such devices can cause rhythmic, fast, low-voltage bursts, which may be confused for spikes.^ It is worth noting, however, that enhanced low voltage, high frequency activity will sometimes presage the larger voltage, low frequency spike and/or wave complexes that define an epileptic event.
  • Predicting Relapse to Alcohol and Drug Abuse via Quantitative Electroencephalography 19 January 2010 18:39 UTC www.nature.com [Source type: Academic]

^ A more specific finding in schizophrenia is a relatively low mean alpha frequency, 98 , 99 although some patients may show a fast alpha rhythm.
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

^ One may achieve entrainment through bursts of sounds such as through drum beats, or one may achieve entrainment through the less direct and more subtle route of binaural beats.
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Artifact correction

.Recently, independent component analysis techniques have been used to correct or remove EEG contaminates.^ Examination of the components before and after correction of ERPs for frontalis muscle activity suggests that contamination did occur, as evidenced by increases in negative potentials after correction of frontal leads.
  • Prepulse Effects as a Function of Cortical Projection System 19 January 2010 18:39 UTC rsimons.psych.udel.edu [Source type: Academic]

^ This heterogeneity has been recently documented in a large sample of medicated, nonmedicated, and never-medicated schizophrenic patients, using cluster analysis based on QEEG variables.
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

^ The midline P30 and P50 were similarly range corrected and analyzed using a 2-Component x 3-SOA ANOVA and for differences in linear and quadratic change over the three SOAs.
  • Prepulse Effects as a Function of Cortical Projection System 19 January 2010 18:39 UTC rsimons.psych.udel.edu [Source type: Academic]

.These techniques attempt to "unmix" the EEG signals into some number of underlying components.^ These techniques, combined with visual analysis of recorded EEG traces, constitute the canon of contemporary clinical electroencephalography.
  • BioMedical Engineering OnLine | Full text | On the methodological unification in electroencephalography 19 January 2010 18:39 UTC www.biomedical-engineering-online.com [Source type: Academic]

^ Herbert Benson in his book The Relaxation Response (1975), surveys some of the major techniques used for eliciting the relaxation response and describes the essential components of these techniques: .
  • Binaural Beat Stimulation Combined with Alpha Biofeedback 19 January 2010 18:39 UTC web-us.com [Source type: Academic]

^ Most techniques for altering the brain state of a subject have concentrated on altering a measure of this state, i.e., the electroencephalogram (EEG) signal.
  • Method and device for producing a desired brain state - Patent 6488617 12 September 2009 8:15 UTC www.freepatentsonline.com [Source type: Reference]

.There are many source separation algorithms, often assuming various behaviors or natures of EEG. Regardless, the principle behind any particular method usually allow "remixing" only those components that would result in "clean" EEG by nullifying (zeroing) the weight of unwanted components.^ Although Couchesne (1978) has argued that P3a and the novels P3 are not the same component, the results of our factor analyses do not allow for such a differentiation.

^ As the EEG pattern in infants and children can vary considerably, an abnormal EEG can be over-reported by those unfamiliar with the EEG patterns of children.
  • EEG (Electroencephalogram) | Epilepsy Action 19 January 2010 18:39 UTC www.epilepsy.org.uk [Source type: General]

^ Since we are only looking to detect signals up to 100Hz, this separation is more than adequate, and the isolated low-pass filter shown on the right with cutoff 160Hz cleans the signal almost completely (See signal output in results).

Abnormal activity

Abnormal activity can broadly be separated into epileptiform and non-epileptiform activity. It can also be separated into focal or diffuse.
.Focal epileptiform discharges represent fast, synchronous potentials in a large number of neurons in a somewhat discrete area of the brain.^ Every moment our brain cells generate millions of nervous impulses (nerve action potentials) and graded potentials (excitatory and inhibitory postsynaptic potentials) in individual neurons.
  • Solving the inverse problem in electroencephalography 19 January 2010 18:39 UTC www.acm.org [Source type: Academic]

^ Event-related brain potentials to semantically inappropriate and surprisingly large words.
  • Steven A. Hillyard - Publications 19 January 2010 18:39 UTC sdepl.ucsd.edu [Source type: Academic]

^ Auditory brain-stem evoked potentials in cat after kainic acid induced neuronal loss.
  • Bibliography of Publications Related to Deafness in Cats 19 January 2010 18:39 UTC www.lsu.edu [Source type: Academic]

.These can occur as interictal activity, between seizures, and represent an area of cortical irritability that may be predisposed to producing epileptic seizures.^ Although clinical seizures are uncommon in autism, epileptiform activity sometimes occurs.
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

^ Temporal and frontal areas may also display an increase in fast activity related to the neuropsychological impairment, which must be distinguished from muscle artifact and often characterizes these records.
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

.Interictal discharges are not wholly reliable for determining whether a patient has epilepsy nor where his/her seizure might originate.^ Paroxysmal discharges (PD) are abnormal transient events that are associated with seizure disorders, ictally or interictally.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

(See focal epilepsy.)
.Generalized epileptiform discharges often have an anterior maximum, but these are seen synchronously throughout the entire brain.^ In the subacute encephalopathy associated with alcoholism, not only are slow waves noted, but epileptiform activity can also be seen, even as periodic lateralized epileptiform discharges (PLEDS).
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

They are strongly suggestive of a generalized epilepsy.
.Focal non-epileptiform abnormal activity may occur over areas of the brain where there is focal damage of the cortex or white matter.^ Only the cerebral cortex is represented in the EEG, other parts of the brain may influence it indirectly but do not contribute to the voltages recorded.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ During an outpatient's standard EEG there may be no abnormal activity occurring in the brain, so several EEGs may be needed.
  • EEG (Electroencephalogram) | Epilepsy Action 19 January 2010 18:39 UTC www.epilepsy.org.uk [Source type: General]

^ In these diseases, gradual severing of the connections that link different brain areas eventually may cause the symptoms of mental and neurological disability.
  • Determining the nature of brain lesions by electroencephalography - Patent 5269315 19 January 2010 18:39 UTC www.freepatentsonline.com [Source type: Academic]

.It often consists of an increase in slow frequency rhythms and/or a loss of normal higher frequency rhythms.^ The BGR consist of predominant 6-8 or 6-10 Hz waves of 10-20 FV amplitude, with superimposed random slower and higher frequencies ( Figure 12 ).
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ For chronic alcoholism, as in the acute stage, an increase in slow activity is often seen.
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

^ Stages of light and deep non-REM sleep are often recognizable by the higher amplitudes and lower frequencies during deep non-REM sleep.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

.It may also appear as focal or unilateral decrease in amplitude of the EEG signal.^ There is a broad consensus that increased focal or diffuse theta, decreased alpha, decreased coherence, and increased asymmetry are common EEG indicators of the postconcussion syndrome.
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

Diffuse non-epileptiform abnormal activity may manifest as diffuse abnormally slow rhythms or bilateral slowing of normal rhythms, such as the PBR.
.More advanced measures of abnormal EEG signals have also recently received attention as possible biomarkers for different disorders such as Alzheimer's disease.^ It is also reasonable to expect sensitivity in these measures to many dysfunctions believed to be abnormal in some psychiatric disorders.
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

^ Biol Psychiatry 1991; 29:211–223 [Medline] Besthorn C, Forstl H, Geiger-Kabisch C, et al: EEG coherence in Alzheimer disease.
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

^ Even more powerful are statistical comparisons between numerous measures from the individual patient and those of age-matched normal subjects or of patient subjects having different diagnoses.
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

[17]

History

A timeline of the history of EEG is given by Swartz.[18] .Richard Caton (1842–1926), a physician practicing in Liverpool, presented his findings about electrical phenomena of the exposed cerebral hemispheres of rabbits and monkeys in the British Medical Journal in 1875. In 1890, Polish physiologist Adolf Beck published an investigation of spontaneous electrical activity of the brain of rabbits and dogs which included rhythmic oscillations altered by light.^ Richard Caton developed a technique for detecting the electrical activity from the exposed surfaces of the brains of living rabbits and monkeys.
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^ British Medical Journal, 2, 278.
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^ He demonstrated his findings at a meeting of the British Medical Association in 1875 and later published them in the British Medical Journal (Caton, 1875).
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.In 1912, Russian physiologist, Vladimir Vladimirovich Pravdich-Neminsky published the first EEG and the evoked potential of the mammalian (dog).^ Sims MH, Laratta LJ, Bubb WJ and Morgan RV. Waveform analysis and reproducibility of visual evoked potentials in dogs.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ The empirical investigation of the operant control of spontaneous and evoked cortical potentials began with the invention of the electroencephalograph (EEG) by Richard Caton around 1875 (Empson, 1986).
  • Binaural Beat Stimulation Combined with Alpha Biofeedback 19 January 2010 18:39 UTC web-us.com [Source type: Academic]

^ Prior PF. EEG monitoring and evoked potentials in brain ischaemia.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

[19] In 1914, Napoleon Cybulski and Jelenska-Macieszyna photographed EEG-recordings of experimentally induced seizures.
.German physiologist and psychiatrist Hans Berger (1873–1941) began his studies of the human EEG in 1920. He gave the device its name and is sometimes credited with inventing the EEG, though others had performed similar experiments.^ Hans Berger is credited with the discovery of the human alpha rhythm in 1924 (Empson, 1986).
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^ With experience, many artifacts can be recognized readily during interpretation; however it is very helpful if the person performing the EEG makes notes on the record about movements or other events observed during recording.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ In 1924 Hans Berger, a German psychiatrist, developed and applied electroencephalographic techniques for use with humans and in 1929 published his first paper on the subject (Empson, 1986).
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His work was later expanded by Edgar Douglas Adrian. In 1934, Fisher and Lowenback first demonstrated epileptiform spikes. .In 1935 Gibbs, Davis and Lennox described interictal spike waves and the 3 cycles/s pattern of clinical absence seizures, which began the field of clinical electroencephalography.^ Auditory evoked magnetic fields: Response amplitude vs. Electroencephalography and Clinical Neurophysiology , 54 , 147-152.
  • Prepulse Effects as a Function of Cortical Projection System 19 January 2010 18:39 UTC rsimons.psych.udel.edu [Source type: Academic]

^ Lopes da Silva F. EEG analysis: theory and practice In: Electroencephalography Basic Principles, Clinical Applications and Related Fields.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ In: Electroencephalography Basic Principles, Clinical Applications and Related Fields.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

.Subsequently, in 1936 Gibbs and Jasper reported the interictal spike as the focal signature of epilepsy.^ Kellaway P, Frost JD, Jr., Crawley JW. Time modulation of ictal and interictal spike-and-wave activity in generalized epilepsy .
  • James D. Frost, Jr., M.D. - Neurology Faculty - Baylor College of Medicine, Houston, Texas 19 January 2010 18:39 UTC www.bcm.edu [Source type: Academic]

^ Shewmon DA , Erwin RJ: The effect of focal interictal spikes on perception and reaction time.
  • D. Alan Shewmon, MD - Epilepsy, EEG 19 January 2010 18:39 UTC brainharmony.org [Source type: Academic]

^ Frost JD, Jr., Hrachovy RA, Glaze DG. Spike morphology in childhood focal epilepsy: relationship to syndromic classification .
  • James D. Frost, Jr., M.D. - Neurology Faculty - Baylor College of Medicine, Houston, Texas 19 January 2010 18:39 UTC www.bcm.edu [Source type: Academic]

.The same year, the first EEG laboratory opened at Massachusetts General Hospital.^ EEG samples shown are from the collection in the clinical EEG laboratory of the Veterinary Medical Teaching Hospital of the School of Veterinary Medicine, University of California Davis (UCD-VMTH).
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ What is the first word in the phrase "epilepsy open garage cat"?: * The factual information on this page has been approved by the EEG department of a UK hospital.
  • EEG (Electroencephalogram) | Epilepsy Action 19 January 2010 18:39 UTC www.epilepsy.org.uk [Source type: General]

^ Generally, an EEG is carried out at an outpatients appointment at the hospital.
  • EEG (Electroencephalogram) | Epilepsy Action 19 January 2010 18:39 UTC www.epilepsy.org.uk [Source type: General]

Franklin Offner (1911–1999), professor of biophysics at Northwestern University developed a prototype of the EEG which incorporated a piezoelectric inkwriter called a Crystograph (the whole device was typically known as the Offner Dynograph).
.In 1947, The American EEG Society was founded and the first International EEG congress was held.^ Joint meeting of the American EEG Society and the American Epilepsy Society, November 11, 1982.
  • D. Alan Shewmon, MD - Epilepsy, EEG 19 January 2010 18:39 UTC brainharmony.org [Source type: Academic]

^ American EEG Society annual meeting, New Orleans, LA, September 23-24, 1989.
  • D. Alan Shewmon, MD - Epilepsy, EEG 19 January 2010 18:39 UTC brainharmony.org [Source type: Academic]

^ Neonatal EEG. Dinner workshop co-presented with Barry R. Tharp, MD, American EEG Society, San Diego, CA, October 4, 1988.
  • D. Alan Shewmon, MD - Epilepsy, EEG 19 January 2010 18:39 UTC brainharmony.org [Source type: Academic]

In 1953 Aserinsky and Kleitman describe REM sleep.
.In the 1950s, William Grey Walter developed an adjunct to EEG called EEG topography which allowed for the mapping of electrical activity across the surface of the brain.^ He is credited with the discovery of the spontaneous EEG in animals and with demonstrating the ability to detect electrical brain responses to stimuli.
  • Binaural Beat Stimulation Combined with Alpha Biofeedback 19 January 2010 18:39 UTC web-us.com [Source type: Academic]

^ Conclusion: Numerous EEG as well as QEEG reports agree that a high proportion of children with developmental disorders—among which learning disabilities and attention-deficit hyperactivity have received the most attention—display abnormal brain electrical activity.
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

^ Considerable attention is currently being given to the correlation of EEG or QEEG brain mapping with other brain functional mapping methods such as PET, SPECT, and MRI. Methods have been developed for the estimation of three-dimensional electrical source distributions in the brain computed from scalp recordings.
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

This enjoyed a brief period of popularity in the 1980s and seemed especially promising for psychiatry. It was never accepted by neurologists and remains primarily a research tool.

Various uses

.The EEG has been used for many purposes besides the conventional uses of clinical diagnosis and conventional cognitive neuroscience.^ A voluminous literature attests to the robustness of conventional EEG studies and their clinical utility in disorders of brain function.
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

^ EEG, first clinically applied in 1929 by the neuropsychiatrist Hans Berger, 258 promises to have greatly expanded use as psychiatrists become more familiar with its many applications.
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

^ Such a high level of specificity is beyond the confidence level achieved by many routinely used clinical tests, such as mammograms, cervical screenings, or CT brain scans.
  • Conventional and Quantitative Electroencephalography in Psychiatry -- Hughes and John 11 (2): 190 -- J Neuropsychiatry Clin Neurosci 19 January 2010 18:39 UTC neuro.psychiatryonline.org [Source type: Academic]

Neurofeedback remains an important extension, and in its most advanced form is also attempted as the basis of brain computer interfaces. The EEG is also used quite extensively in the field of neuromarketing. There are many commercial products substantially based on the EEG.
Honda is attempting to develop a system to move its Asimo robot using EEG, a technology which it eventually hopes to incorporate into its automobiles.[20]
EEGs have been used as evidence in trials in the Indian state of Maharastra.[21]

EEG and Telepathy

DARPA has budgeted $4 million in 2009 to investigate technology to enable soldiers on the battlefield to communicate via computer-mediated telepathy. The aim is to analyse neural signals that exist in the brain before words are spoken. [22]

Games

  • Announced at the turn of 2008/2009 were two one-player tabletop gadgets, based on the EEG technology of the company Neurosky. MindFlex by Mattel consists of a ball on a small obstacle course,[24] Force Trainer by Uncle Milton Industries of a ball in a transparent tube.[25] Both feature a headset and a motor to levitate the ball.

Images

See also

References

  1. ^ E. Niedermeyer, Lopes da Silva, F., Electroencephalography, 4th Ed., 1999, Williams & Wilkins, Baltimore, MD, 1258 pp.
  2. ^ Atlas of EEG & Seizure Semiology. B. Abou-Khalil; Musilus, K.E.; Elsevier, 2006.
  3. ^ Creutzfeldt OD, Watanabe S, Lux HD (1966). "Relations between EEG phenomena and potentials of single cortical cells. I. Evoked responses after thalamic and epicortical stimulation". Electroencephalogr Clin Neurophysiol 20 (1): 1–18. doi:10.1016/0013-4694(66)90136-2. PMID 4161317. 
  4. ^ a b Nunez PL, Srinivasan R (1981). Electric fields of the brain: The neurophysics of EEG. Oxford University Press. 
  5. ^ Hamalainen M, Hari R, Ilmoniemi RJ, Knuutila J, Lounasmaa OV (1993). "Magnetoencphalography - Theory, instrumentation, and applications to noninvasive studies of the working human brain". Reviews of Modern Physics 65: 413–497. doi:10.1103/RevModPhys.65.413. 
  6. ^ Buzsaki G (2006). Rhythms of the brain. Oxford University Press. 
  7. ^ Klein, S., & Thorne, B. M. (2007). Biological psychology. New York, N.Y.: Worth.
  8. ^ Whittingstall K, Logothetis NK. (2009). Frequency-band coupling in surface EEG reflects spiking activity in monkey visual cortex. Neuron. 64(2):281-9. PMID 19874794
  9. ^ Towle VL, Bolaños J, Suarez D, Tan K, Grzeszczuk R, Levin DN, Cakmur R, Frank SA, Spire JP. (1993). "The spatial location of EEG electrodes: locating the best-fitting sphere relative to cortical anatomy". Electroencephalogr Clin Neurophysiol 86 (1): 1–6. doi:10.1016/0013-4694(93)90061-Y. PMID 7678386. 
  10. ^ Niedermeyer E, Lopes da Silva F (2004). Electroencephalography: Basic Principles, Clinical Applications, and Related Fields. Lippincot Williams & Wilkins. 
  11. ^ H. Aurlien, I.O. Gjerde, J. H. Aarseth, B. Karlsen, H. Skeidsvoll, N. E. Gilhus (March 2004). "EEG background activity described by a large computerized database.". Clinical Neurophysiology 115 (3): 665–673. doi:10.1016/j.clinph.2003.10.019. PMID 15036063. 
  12. ^ Nunez PL, Pilgreen KL (1991). "The spline-Laplacian in clinical neurophysiology: a method to improve EEG spatial resolution". J Clin Neurophysiol 8 (4): 397–413. PMID 1761706. 
  13. ^ J. Anderson, Cognitive Psychology and It's Implications, 6th Ed., 2005, Worth Publishers, New York, NY, 17 pp.
  14. ^ Cahn BR, & Polich J. (2006). Meditation states and traits: EEG, ERP, and neuroimaging studies. Psychological Bulletin. 132 (2), 180-211.
  15. ^ Pfurtscheller G, Lopes da Silva FH (1999). "Event-related EEG/MEG synchronization and desynchronization: basic principles". Clin Neurophysiol 110 (11): 1842–1857. doi:10.1016/S1388-2457(99)00141-8. PMID 10576479. 
  16. ^ Epstein, Charles M. (1983). Introduction to EEG and evoked potentials. J. B. Lippincot Co.. ISBN 0-397-50598-1. 
  17. ^ Montez T, Poil S-S, Jones BF, Manshanden I, Verbunt JPA, van Dijk BW, Brussaard AB, van Ooyen A, Stam CJ, Scheltens P, Linkenkaer-Hansen K (2009). "Altered temporal correlations in parietal alpha and prefrontal theta oscillations in early-stage Alzheimer disease". PNAS 106 (5): 1614–1619. doi:10.1073/pnas.0811699106. http://www.pnas.org/content/106/5/1614.abstract. 
  18. ^ Swartz, B.E; Goldensohn, ES (1998). "Timeline of the history of EEG and associated fields" (PDF). Electroencephalography and clinical Neurophysiology 106 (2): 173–176. doi:10.1016/S0013-4694(97)00113-2. PMID 9741779. http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6SYX-4FV4S6H-1-1&_cdi=4846&_user=10&_orig=browse&_coverDate=02%2F28%2F1998&_sk=998939997&view=c&wchp=dGLbVzz-zSkWb&md5=47fbbe7e51a806779716fba415b96ab7&ie=/sdarticle.pdf. 
  19. ^ Pravdich-Neminsky VV. Ein Versuch der Registrierung der elektrischen Gehirnerscheinungen (In German). Zbl Physiol 27: 951–960, 1913.
  20. ^ [1] 1 Apr 20009, Japan Times
  21. ^ This brain test maps the truth 21 Jul 2008, 0348 hrs IST, Nitasha Natu,TNN
  22. ^ Katie, Drummond; Noah Schachtman (2009-05-14). "Pentagon Preps Soldier Telepathy Push". Wired. http://www.wired.com/dangerroom/2009/05/pentagon-preps-soldier-telepathy-push/. Retrieved 2009-06-14. 
  23. ^ "Emotiv Systems Homepage". Emotiv.com. http://emotiv.com/. Retrieved 2009-12-29. 
  24. ^ http://www.physorg.com/news150781868.html
  25. ^ http://www.usatoday.com/life/lifestyle/2009-01-06-force-trainer-toy_N.htm

External links


Study guide

Up to date as of January 14, 2010

From Wikiversity

.Electroencephalography (EEG) measures the electrical activity of the cerebral cortex at the time of the scan.^ The EEG is a record of the spontaneous electrical activity of the cerebral cortex; no stimulation is necessary to record it.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

^ The history of electroencephalography, the measurement and study of the brain's electrical activity, dates back to the mid- to late nineteenth century when advances made in the science of electromagnetism began to be applied to human physiology.
  • Binaural Beat Stimulation Combined with Alpha Biofeedback 19 January 2010 18:39 UTC web-us.com [Source type: Academic]

^ Only the cerebral cortex is represented in the EEG, other parts of the brain may influence it indirectly but do not contribute to the voltages recorded.
  • Clinical Electroencephalography in Dogs (1999) - Issue 1 - Volume 1 - Vet Neurol Neurosurg J 19 January 2010 18:39 UTC www.vin.com [Source type: Academic]

.The measurements are usually taken using electrodes that are placed on the scalp.^ The electrode head box is shown connected with the head of the patient whereby electrical measurements are taken by electrodes 13 from the brain of the patient.
  • Diagnosing brain conditions by quantitative electroencephalography - Patent 5230346 19 January 2010 18:39 UTC www.freepatentsonline.com [Source type: Academic]

^ The system most often used to place electrodes for monitoring is the International Federation 10-20 System as illustrated in Figure 4 .

^ Scalp electrodes are able to measure this value with poor spatial resolution.

.Neural activity generates electric field potentials in the brain which can be measured, these usually appear as regular rhythms at different frequencies on the EEG trace.^ Measurement and analysis of brain magnetic field.
  • I-LABS: Toshiaki Imada, Ph.D. - Publications 19 January 2010 18:39 UTC ilabs.washington.edu [Source type: Academic]

^ The origin of action potentials can be traced to the electrical activity at the cellular level.

^ Behavior and brain electrical activity.
  • James D. Frost, Jr., M.D. - Neurology Faculty - Baylor College of Medicine, Houston, Texas 19 January 2010 18:39 UTC www.bcm.edu [Source type: Academic]


Citable sentences

Up to date as of December 25, 2010

Here are sentences from other pages on Electroencephalography, which are similar to those in the above article.








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