Electrophysiological analysis of conditioned taste aversion in rats

The memory mechanisms of conditioned taste aversion (CTA) were examined using electrophysiological methods. Presentation of the aversive taste to CTA trained animals inhibited unit activity in gustatory cortex, amygdala and ventromedial hypothalamus and caused delayed excitation of neurons in lateral hypothalamus. Lick-triggered rewarding stimulation of medial forebrain bundle substituted the taste CS in CTA experiments. The same stimulation triggered by nose-poking failed to be associated with subsequent poisoning. Importance of specific brain areas for CTA retrieval was assessed by the effect of lick-triggered stimulation of the examined site on gustatory discrimination. The disruption threshold was lowest in amygdala and lateral hypothalamus. Stimulation of other brain structures did not interfere with gustatory discrimination at current intensities subthreshold for disruption of licking. Unilateral electrical stimulation of vestibular nuclei following ingestion of saccharin elicited marked aversion to this taste.