Behavioral and Electrophysiological Studies of Absence Epilepsy

Abstract

Systematic study of the altered behavioral state seen in absence epilepsy began 50 years ago with the investigations of reaction time performance, conducted by Schwab (1939). He found, in patients suffering from absence attacks, that prolonged delays in responding to auditory or visual stimuli occurred during the time of their characteristic paroxysmal wave-spike (WS) discharges. In some instances, patients failed to respond during WS paroxysms. In their theoretical exposition of centren-cephalic epilepsy, Penfield and Jasper (1954) accounted for observations such as Schwab’s as reflections of perturbations in the functioning of a widespread system, headquartered in the brain stem, responsible for the maintenance of consciousness. According to this concept, which stemmed in part from the writings of Hughlings Jackson, there exists within the brain a region that forms the “neural substratum of consciousness,” i.e., the highest level of functional integration of sensory and motor processes. Furthermore, seizures in this region are accompanied by unconsciousness (Penfield and Jasper, 1954). This view was certainly compatible with that of Moruzzi and Magoun (1949), who described the functions of the brain-stem reticular formation. The grand Jacksonian concept of Penfield and Jasper has influenced the research and thinking of many neuroscientists, not only about the pathogenesis of the absence disorder but also about the nature of the behavioral disturbance itself.