Evidence is presented to suggest that the hippocampus receives 2 nonspecific inputs from the brainstem, each capable of producing rhythmical slow activity. The neocortex appears to receive 2 similar inputs, each capable of producing low voltage fast activity. One input to both hippocampus and neocortex is blocked by atropine and stimulated by eserine, and is essentially unrelated to concurrent motor activity. A second input to both hippocampus and neocortex is resistant to atropine, is depressed by phenothiazines, and is activated by d-amphetamine. Activity in this system is closely related to concurrent "voluntary" movement.