ELECTROENCEPHALOGRAPHY AND CLINICAL NEUROPHYSlOLOGY

The main focus of the self-stimulation phenomenon, as indicated by maximum rates for minimum stimulus levels and by lesion studies, iies in an olfactory midbrain pathway through septal area, lateral hypothalamus and ventrolateral tegmemum; over most of its course this pathway is called the medial forebrair bundle. The studies which indicated this "focus" also showed a gradient of self-stimulation along its course; the ordering of its subdivisions in terms of the rate and regularity of the self-stimulation behavior produced by stimulating them was (!) ventrolaterai tegmentum which headed the list, (2) posterior lateral hypothalamus, (3) anterior lateral hypothalamus, and (4) septal area (Olds et ai. 1960, Olds and OIds 1963; OIds and Olds 1964). These studies utilized rat, but the same regions were salient in studies with cat (Wilkinson and Peele 1963) and monkey (Bursten and Delgado 1958; Briese and Olds 1964). Minor areas of self-stimulat.ion were found in parts of rhinencephalon and thalamus (OIds 1956). Because of the suggestion that rhinencephalic and thalamic self-stimulation might be correlated with epileptiform activity (Porter et al. 1959; Newman and Feldman 1964), it seemed reasonable to find whether self-stimulation in the main focus would produce epileptiform activity and whether a correlation in threshold or intensity could be observed between after-discharges or seizures and self-stimulation. The present study