Neuropsychology

Neuropsychology is a specialization within the field of psychology that examines brain–behavior relationships. The ability to determine these relationships rests on clearly defined behaviors and related neuroanatomical structures, neurophysiological mechanisms, and/or neurochemical processes. The field originated from medical science conducted during the 19th century, but a majority of the progress has occurred within the past 40 years, and significant contributions to the field have been made by psychologists working in both clinical and research areas. The knowledge in this field is fast growing but derived almost exclusively from work with hearing people. There has been a paucity of research with deaf individuals, especially those who identify with Deaf culture and have acquired American Sign Language (ASL) or another sign language as their native/preferred language. Initial studies conducted during the 1980s and 1990s primarily examined the neural mechanisms underlying language functioning in deaf signing individuals. More recently, researchers have started to examine the neural mechanisms underlying perception, memory, attention, and executive functioning.

Although the field of neuropsychological research with both native and nonnative deaf individuals is in its infancy, several studies suggest that the global architecture (e.g., structure and pathways) of the brain is similar to that in hearing individuals. Some degree of neural reorganization, however, may occur for specific sensory, motor, and cognitive functions in both native and nonnative deaf individuals. Although somewhat controversial, emerging evidence suggests that this neural reorganization may stem from native acquisition of ASL versus spoken English. It is still unclear, however, the extent to which such reorganization results in functional differences in behavior.

The field of clinical neuropsychology focuses on evaluating changes in cognition, behavior, and emotion subsequent to an acquired injury to brain structures and systems (e.g., age-related deficits, vascular injury, traumatic brain injury, and infectious processes). The subspecialty of pediatric or child neuropsychology focuses on understanding brain–behavior relationships in children and adolescents with congenital disorders (e.g., intellectual disability, autism spectrum disorders, learning disabilities, and language disorders) or acquired brain injury [Page 716](e.g., meningitis, traumatic brain injury, sports-related concussions, and epilepsy). Clinical neuropsychologists assist in the diagnostic process, as well as in the development and use of various cognitive and behavioral treatments. Approaches to the assessment process include using a battery of objective tests to evaluate the effects of brain damage on various sensory and motor functions, cognitive functioning (e.g., visual-perception, language, learning, memory, attention, executive functioning), academic achievement, behavioral functioning, emotional functioning, and/or social skills. The remainder of this entry focuses on the application of clinical neuropsychology to the assessment of both native and nonnative deaf individuals.