From Wikibooks, the open-content textbooks collection

Biological psychology is the scientific study of the biological bases of behavior and mental states. Because all behavior is controlled by the central nervous system, it is sensible to study how the brain functions in order to understand behavior. This is the approach taken in behavioral neuroscience, cognitive neuroscience, and neuropsychology. Neuropsychology is the branch of psychology that aims to understand how the structure and function of the brain relate to specific behavioral and psychological processes. Often neuropsychologists are employed as scientists to advance scientific or medical knowledge. Neuropsychology is particularly concerned with the understanding of brain injury in an attempt to work out normal psychological function.

The approach of cognitive neuroscience to studying the link between brain and behavior is to use neuroimaging tools, such as fMRI, to observe which areas of the brain are active during a particular task.