Electrical Stimulation of the Cerebral Cortex in Humans

After centuries of the theoretical assignment of soul, mind, and bodily functions to various anatomical places, the mid-nineteenth century experienced an explosion of information that allowed accurate cerebral localization to begin. The British philosopher Herbert Spencer anticipated the developments of the next 50 years when he wrote in 1855, “Localization of function is the law of all organization whatever: separation of duty is universally accompanied with separateness of structure: and it would be marvelous were an exception to exist in the cerebral hemispheres” (Haymaker and Schiller, 1970). John Hughlings Jackson, a Spencer student, used clinical observations in patients with epilepsy to begin substantiating theories of cerebral localization, and to define brain regions related to specific functions. Broca, Wernicke, Charcot, and the other great neurologists of the late nineteenth century expanded on these beginnings.