The role of focal epilepsy in the development of jacksonian localization

In the 1860s John Hughlings Jackson (1835-1911) reasoned on theoretical grounds that voluntary movements probably were represented in the human cerebral cortex. He then studied the clinical phenomenologies and pathological associations of human focal motor epileptic seizures, post-epileptic hemiplegia and aphasia, and also chorea. From these various lines of evidence he concluded by 1870 that voluntary movement of the face and upper limb on the opposite side were represented in a localized area of the human cerebral cortex overlying the corpus striatum. He recognized this shortly before the physiologists demonstrated such cortical localization of function in experimental animals. Over the following three decades, Jackson analyzed the spread of focal motor epileptic seizure activity, and the phenomenology of other types of epileptic seizure in humans, and related this knowledge to the sites of the brain pathology that appeared responsible for these events. This enabled him to locate cerebral cortical sites for the representation of foot movement, consciousness, and various aspects of special sensory function, as well as for certain psychic phenomena that arose from temporal lobe paroxysmal disturbance.