The application of neuroscience to clinical interventions rests on the premise that different parts of the brain carry out different tasks related to elements of cognition, emotion, and behavior. A client's words and actions during therapy provide information regarding which brain systems are active during therapy and the strengths and weaknesses in these different brain systems. An understanding of underlying brain processes can guide conceptualization of the client's functioning, choices of intervention, and communication with the client during interventions.

Neuropsychology is a field that links observed behaviors to the areas of the brain used in carrying out those behaviors (Lezak, Howieson & Loring, 2004). In its early days, a primary application of neuropsychological assessment involved the use of behavioral observations and tests to help determine the location of damage within the brain. These determinations guided surgical as well as rehabilitation interventions. In recent years, imaging techniques (see Appendix) have been developed that allow non-intrusive examination of brain structure and function, minimizing the need to rely on neuropsychological behavior-based tests for locating brain lesions. However, the idea that specific parts of the brain support specific behaviors remains a powerful guide to understanding the nature of clients' functioning and intervening to help them.

The basic concept underlying neuropsychological assessment is that each behavior relies on activity in a specific set of areas of the brain, and that each area of the brain is involved in only certain types of behavior.