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Brain: Dentate gyrus
HippocampalRegions.jpg
Diagram of hippocampal regions. DG: Dentate gyrus.
Gray717.png
Coronal section of brain immediately in front of pons. (Label for "Gyrus dentatus" is at bottom left.)
Latin gyrus dentatus
Gray's subject #189 827
Part of Temporal lobe
Artery Posterior cerebral
Anterior choroidal
NeuroNames hier-161
MeSH Dentate+Gyrus
NeuroLex ID birnlex_1178

The dentate gyrus is part of the hippocampal formation. It is thought to contribute to new memories as well as other functional roles.[1][2] It is notable as being one of a select few brain structures currently known to have high rates of neurogenesis in adult humans,[3] (other sites include the olfactory bulb and cerebellum).[4][5]

Contents

Structure

The dentate gyrus consists of three layers of neurons: molecular, granular, and polymorphic. The middle layer is most prominent and contains granule cells that project to the CA3 subfield of the hippocampus.[6] These granule cells project mostly to interneurons, but also to pyramidal cells and are the principal excitatory neurons of the dentate gyrus. The major input to the dentate gyrus (the so-called perforant pathway) is from layer 2 of the entorhinal cortex, and the dentate gyrus receives no direct inputs from other cortical structures. The perforant pathway is divided into the medial perforant path and the lateral perforant path, generated, respectively, at the medial and lateral portions of the entorhinal cortex. The medial perforant path synapses onto the proximal dendritic area of the granule cells, whereas the lateral perforant path does so onto the distal dendrites of these same cells.

Function

Phenotypes of proliferating cells in the dentate gyrus. A fragment of an illustration from Faiz et al., 2005.[7]

The dentate gyrus is thought to contribute to the formation of memories and to play a role in depression.

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Memory

The dentate gyrus is one of the few regions of the adult brain where neurogenesis (i.e., the birth of new neurons) takes place. Neurogenesis is thought to play a role in the formation of new memories. New memories could preferentially utilize newly-formed dentate gyrus cell, providing a potential mechanism for distinguishing multiple instances of similar events or multiple visits to the same location.

Stress and Depression

The dentate gyrus may also have a functional role in stress and depression. For instance, neurogenesis has been found to increase in response to chronic treatment with antidepressants[8]. On the contrary, however, the physiological effects of stress, often characterized by release of glucocorticoids such as cortisol, as well as activation of the sympathetic division of the autonomic nervous system, have been shown to inhibit the process of neurogenesis in primates[9]. Both endogenous and exogenous glucocorticoids are known to cause psychosis and depression,[10], implying that neurogenesis in the dentate gyrus may play an important role in modulating symptoms of stress and depression.

Other

Some evidence suggests that neurogenesis in the dentate gyrus increases in response to aerobic exercise[11].

Blood Sugar

Studies by researchers at Columbia University Medical Center indicate that poor glucose control can lead to deleterious effects on the dentate gyrus.[12]

References

  1. ^ Helen Scharfman, ed (2007). The Dentate Gyrus: A comprehensive guide to structure, function, and clinical imiplications. 163. 1-840.  
  2. ^ Saab BJ, Georgiou J, Nath A, Lee FJ, Wang M, Michalon A, Liu F, Mansuy IM, Roder JC. (2009). "NCS-1 in the dentate gyrus promotes exploration, synaptic plasticity, and rapid acquisition of spatial memory.". Neuron 63 (5): 643-56. doi:10.1016/j.neuron.2009.08.014. PMID 19755107.  
  3. ^ Cameron HA, McKay RD (2001). "Adult neurogenesis produces a large pool of new granule cells in the dentate gyrus". J Comp Neurol 435 (4): 406–17. doi:10.1002/cne.1040. PMID 11406822.  
  4. ^ Graziadei PP, Monti Graziadei GA (1985). "Neurogenesis and plasticity of the olfactory sensory neurons". PLoS ONE 457: 127–42. PMID 3913359.  
  5. ^ Ponti G, Peretto B, Bonfanti L (2008). "Genesis of neuronal and glial progenitors in the cerebellar cortex of peripuberal and adult rabbits". PLoS ONE 3 (6): e2366. doi:10.1371/journal.pone.0002366. PMID 18523645.  
  6. ^ Nolte, John (2002). The Human Brain: An Introduction to Its Functional Neuroanatomy (fifth ed.). pp. 570–573.  
  7. ^ Faiz M, Acarin L, Castellano B, Gonzalez B (2005). "Proliferation dynamics of germinative zone cells in the intact and excitotoxically lesioned postnatal rat brain". BMC Neurosci 6: 26. doi:10.1186/1471-2202-6-26. PMID 15826306. PMC 1087489. http://www.biomedcentral.com/1471-2202/6/26.  
  8. ^ Malberg JE, Eisch AJ, Nestler EJ, Duman RS (2000). "Chronic antidepressant treatment increases neurogenesis in adult rat hippocampus". J. Neurosci 20 (24): 9104–9110. PMID 11124987.  
  9. ^ Gould E, Tanapat P, McEwen BS, Flugge G, Fuchs E (1998). "Proliferation of granule cell precursors in the dentate gyrus of adult monkeys is diminished by stress". PNAS 95 (6): 3168–3171. doi:10.1073/pnas.95.6.3168. PMID 9501234.  
  10. ^ Jacobs B, Praag H, Gage F (2000). "Adult brain neurogenesis and psychiatry: a novel theory of depression". Mol. Psychiatry 5 (3): 262–9. doi:10.1038/sj.mp.4000712. PMID 10889528.  
  11. ^ Kempermann G, Kuhn HG, Gage FH, (1997). "More hippocampal neurons in adult mice living in an enriched environment". Nature 386 (6624): 493–495. doi:10.1038/386493a0. PMID 9087407.  
  12. ^ http://www.nytimes.com/2009/01/01/health/31memory.html?_r=1&em=&pagewanted=print Blood Sugar Control Linked to Memory Decline, Study Says

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