Electrical activity of the hippocampus during delayed responses and hypothalamic stimulation in the cat.

Electrical activity of hippocampus was investigated in cats in the delayed response situation by comparing spectral analysis and integration of electrohippocampogram rhythms in different stages of delayed response performance. In addition, electrical stimulation of lateral and ventromedial hypothalamic nuclei was used to observe changes in the hippocampal theta rhythm, as well as the behavioral effect during the delayed response performance. It is concluded that changes in the hippocampal theta rhythm are related to the changes in the drive level: high drive results in increasing the theta rhythm, whereas drive reduction results in its suppression. The activating role of hypothalamus in the dynamic changes occurring in the limbic circuit and their function in solving the delayed response problem are widely discussed.