Functional relations between the cortical gustatory area and the amygdala: electrophysiological and behavioral studies in rats.

The functional interconnections between the cortical gustatory area (CGA) and the amygdala were examined by electrophysiological and behavioral experiments in rats. The cortical neurons responsive to taste stimuli applied to the anterior part of the tongue were located in the Vth layer of the agranular insular cortex. Of a total of 27 cortical neurons recorded, 10 showed facilitatory and/or inhibitory responses with the mean onset latency of about 20 msec to electrical stimulation of the ipsilateral amygdala. On the other hand, of 18 amygdaloid neurons responsive to taste stimuli, 13 showed facilitatory and/or inhibitory responses to electrical shocks to the ipsilateral CGA, with a mean latency of about 16 ms. No cortical and amygdaloid neurons sampled responded antidromically to the electrical stimulation. These results suggest the existence of mutual polysynaptic fiber connections between the CGA and the amygdala. The behavioral experiment was performed by means of a conditioned taste aversion (CTA) technique. After acquisition of CTA to sucrose solution by pairing it with an i.p. injection of LiCl which produces sickness, bilateral small knife cuts between the CGA and the amygdala in the perirhinal region disrupted retention of CTA. Thus, these interconnections may play some role in association of taste-related cognitive processes with feeding behavior.