Influence of stimulation of the medial hypothalamus on the interaction of neurons of the rabbit neocortex.

The interaction of neurons of the visual and sensory motor areas of the neocortex of the rabbit before and after stimulation of some medial nuclei of the hypothalamus was investigated by plotting cross- and autocorrelation histograms. Stimulation through bipolar electrodes using bursts of biphasic pulses at a frequency of 100 Hz, current strength 50-200 microA, led to the appearance in freely behaving rabbits of the reaction of avoidance of the place of stimulation. Following stimulation, as compared with resting wakefulness, the number of pairs of neurons functioning in correlation increased to 45%; at the same time, discharges of neurons of the sensory motor area ran ahead of discharges of visual neurons in the pairs up to 120 msec; the periodicity of the coupled discharges was mainly in the theta frequency range. A conclusion regarding the reflection of defense motivation in certain indices of the interaction of the cortical cells in the presence of a tonic conditioned reflex is reached on the basis of a comparison of the interaction of neurons following stimulation of the medial hypothalamus and the midbrain reticular formation, in the intersignal periods during the development of a defense conditioned reflex as well.