One of the chief clinical assets of electroencephalography is its power to localize gross cortical lesions. The early work of Berger1 and of Foerster and Altenburger2 called attention to the possibilities of the method, but the practical value of electroencephalography for the localization of gross lesions prior to operation was first clearly demonstrated by Walter.3 The closely related problem of localization of a discharging lesion or seizure focus was the subject of early reports by Jasper4 and by Gibbs, Lennox and Gibbs5 and of later reports by Jasper and Hawke6 and by Casamajor and his co-workers.7 Reviews of the literature on electroencephalographic localization and lengthy bibliographies have been published elsewhere.8
As a result of their studies, Jasper and his associates9 concluded that the most important characteristics of a seizure discharge are the degree and direction of spread. Jasper proposed that seizure