Abstract
1. The two types of electrical activities of the hippocampus evoked by direct stimulation of the brain have been studied in unanesthetized rabbits, immobilized by tubocurarine.
2. The slow wave pattern of the hippocampal electrical activity, characterized by the regular slow waves at 5 to 7 cycles per second, was induced by direct stimulation of the medial preoptic area, medial hypothalamic region, central gray matter and dorso-lateral part of the tegmentum of the midbrain.
3. The fast wave pattern of the hippocampal electrical activity, characterized by low voltage fast waves at 15 to 30 cycles per second, was elicited by direct stimulation of the medial septum, lateral hypothalamus and medio-ventral part of the tegmentum of the midbrain.
4. The slow and fast wave pattern of the hippocampal electrical activity may represent activity of the separate system within the brain, sympathetic and parasympathetic activities.
