brain localization theory
any of various theories that different areas of the brain serve different functions. Since the early 19th century, opinion has varied between notions of highly precise localization and a belief that the brain, or large portions of it, function as a whole. In 1861, Paul Broca deduced from localized brain lesions that the speech center of the brain is in the left frontal lobe (see Broca’s area). Since then, many techniques, including localized electrical stimulation of the brain, electrical recording from the brain, and brain imaging, have added information about localization of function in the brain. For many investigators, however, the concept of extreme parcellation of functions has given way to concepts of distributed control by collective activity of different regions. See also mass action.