This article addresses the discrepancy between Edouard Hitzig\'s and David Ferrier\'s findings on the cortical localization of movements in animals and Jean-Martin Charcot\'s findings in humans. The results of Hitzig\'s and Ferrier\'s vivisections were criticized by experimentalists in England and France as discordant, irreproducible, and inconclusive, and they were rejected by clinicians as irrelevant. Charcot addressed the gap between animal and human motor function by correlating motor deficits and focal epileptic seizures in patients to their autopsy findings. By this method he discovered the functional organization of the human motor cortex and produced the first accurate human motor brain map. Ferrier, William Osler, and Hughlings Jackson acknowledged Charcot\'s findings, and his findings guided the first neurosurgeons in localizing and resecting intracranial mass lesions presenting with focal epileptic seizures. Although his contributions in these fields have been neglected by modern historians, Charcot made significant contributions to the neurobiology of the human motor system, to epileptology, and to the birth of modern neurosurgery.

This article is an outline of the transition in \"brain maps\" used to illustrate locations of cortical \"centers\" associated with movements, sensations, and language beginning with images from Gall and Spurzheim in the nineteenth century through those of functional magnetic resonance imaging in the twenty-first century. During the intervening years, new approaches required new brain maps to illustrate them, and brain maps helped to objectify and naturalize mental processes. One approach, electrical stimulation of the cerebral cortex-exemplified by Fritsch and Hitzig in 1870, Ferrier in 1873, and Penfield by 1937-required brain maps showing functional centers with expanded and overlapping boundaries. In another approach, brain maps that linked cortical centers to account for the complex syndromes of aphasia, apraxia, alexia, and agraphia were initially constructed by Baginsky in 1871, Wernicke in 1874, and Lichtheim in 1885, then later by Lissauer in 1890, Dejerine in 1892, and Liepmann in 1920, and eventually by Geschwind in 1965 and others through the late twentieth century. Over that intervening time, brain maps changed from illustrations of points on the cerebral cortex where movements and sensations were elicited to illustrations of areas (centers) associated with recognizable functions to illustrations of connections between those areas that account for complex symptoms occurring in clinical patients. By the end of this period, advancements in physics, mathematics, and cognitive science resulted in inventions that allowed brain maps of cortical locations derived from cognitive manipulations rather than from the usual electrical or ablative manipulations. \"Mental\" dependent variables became \"cognitive\" independent variables.

There was an increasing medical interest in the localization of representation of function in the cerebral cortex after Broca in 1861 identified a cortical area that appeared responsible for expressive speech. By the late 1860s, John Hughlings Jackson-based on clinico-pathological correlations mainly in persons with focal motor seizures-had reasoned that contralateral somatic motor function was represented in another area of the cortex. This localization was supported by Fritsch and Hitzig (1870) in experimental cortical stimulation studies in dogs. These authors also reported producing events resembling contralateral motor convulsing in their animals. Their work, and Jackson\'s ideas, prompted David Ferrier, in Great Britain, to begin a program of cerebral cortical stimulation studies in various vertebrate species, trying to locate cortical sites of representation of functions other than expressive speech and motor activity. In his initial report of his investigations (1873), he noted that appropriately sited Faradic stimulation evoked immediate or delayed contralateral focal motor seizures, some of which evolved into generalized convulsions. On this basis he reasoned that focal motor and generalized seizures were expressions of the same disorder; that nearly all epilepsies originated in the cerebral cortex and not in the lower brain stem, as hitherto thought; and that the clinical pattern of epileptic seizure phenomenology depended on the function of the cortical site of origin and the extent and direction of spread of seizure activity in the brain. He not only provided experimental verification for Jackson\'s reasoning about epileptic seizure mechanisms but expressed the ideas a good deal more clearly than Jackson ever managed to do. Ferrier\'s achievement in this regard has tended to escape notice, lost sight of because of the great importance of his investigations into localization of cerebral function.