Ibotenic acid lesions of the basolateral, but not the central, amygdala interfere with conditioned taste aversion: Evidence from a combined behavioral and anatomical tract-tracing investigation

Rats (Rattus norvegicus) with almost complete ibotenic acid lesions (at lea st 90%) of the basolateral amygdaloid complex (BLA) failed to learn a condi tioned taste aversion (CTA; Experiment 1A). In these same BLA rats, the bid irectional parabrachial-insular pathway that courses through the central nu cleus of the amygdala (Ce) was shown to be spared (Experiment 1B), indicati ng that the BLA per se is critical for CTA learning. In contrast to the del eterious effect of BLA lesions on CTA, ibotenic acid lesions of the Ce did not block CTA learning (Experiment 2). Nonreinforced preexposure to the gus tatory stimulus attenuated CTA acquisition in normal rats, and, under these conditions, rats with BLA lesions were no longer impaired (Experiment 3). Thus, ibotenic acid lesions centered over the Ce, sparing a considerable ex tent of the BLA, together with the testing procedure used in previous exper iments (e.g., L. T. Dunn & B. J. Everitt, 1988), led to the belief that the CTA deficits reported after electrolytic lesions of the amygdala were the result of incidental damage to fibers of passage.