Cortical epileptogenesis and David Ferrier

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.