Responses of the neurons of the lateral and ventromedial hypothalamic regions (HL and Hvrn, respectively), as well as of the area of the dorsal hypothalamus (arid) and the projection region of the medial forelimb bundle (MFB), evoked by stimulation of the proreal cortex (field 8), cingular cortex (field 24), pyriform Iobula (periamigdalar cortex), and hippocampus (CA3) were studied in acute experiments on cats under ketamine anesthesia. Distributions of the latent periods of the responses recorded from hypothalamic neurons at stimulation of the above cortical structures were analyzed. The responses were classified into primary excitatory and primary inhibitory. Stimulation of the proreal gyrus evoked four times more excitatory responses than inhibitory responses. With stimulation of the cingular gyrus, the ratio of excitatory/inhibitory responses was 1.5:1. Stimulation of the pyriform cortex evoked activatory and inhibitory responses with a similar probability. With hippocampal stimulation, inhibitory responses appeared two times more frequently than excitatory reactions. The hypothalamus was found to be a zone of wide convergence: one-half of all responding neurons in the HL and Hvm responded to stimulations of two or more tested cortical zones. In 26~o of the cells, only excitatOry convergence was observed, while in 10~o only inhibitory convergence was found; 21 ~/~, of the cells revealed mixed convergence.
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