Effects of feedback caudate nucleus stimulation on spontaneous fast amygdaloid spindles and drive

Experiments with single and repetitive stimulation of the head of the caudate nucleus (4-10 V, 0.3 msec) triggered by occurrence of fast amygdaloid spindles (35 c/s microV, 0.5 sec) were performed in six animals with chronically implanted cerebral electrodes. In conjunction with the anterior cortical recruiting response the stimulation increased the incidence of amygdaloid fast spindles and decreased the incidence of hippocampal theta activity and of searching eye movements. The associative training failed, however, to significantly modify in the background EEG, the mean incidence of the fast amygdaloid spindles or the rate of the sensorimotor rhythm of 12-18 c/s. Its only effect (after long repetition) was a displacement to the right of the regression line of the incidence of the two rhythms and a slight alteration in the slope. The possibility of activating the caudate nucleus inhibitory effects through the amygdala during internal inhibition phenomena is discussed.