Thalamocortical relations in taste aversion learning: I. Involvement of gustatory thalamocortical projections in taste aversion learning.

The anterior insular gustatory neocortex (AIGN) has been implicated as a functional substrate of conditioned taste aversion (CTA) learning. Results of previous neuroanatomical and neurobehavioral experiments indicate that projections from gustatory-responsive neurons in the posterior ventromedial thalamic nuclei (parvicellular division; VPMpc) may provide relevant input to the AIGN during CTA learning. In rat, gustatory thalamocortical projections from VPMpc thalamus traverse the ventrolateral neostriatum (VLS) enroute to the AIGN. In these experiments, various neuroanatomical and neurobehavioral manipulations in the VLS were used to examine the contribution of presumed gustatory thalamocortical projections to CTA learning. These experiments demonstrate that projections from VPMpc thalamus to the AIGN are essential for normal CTA learning. Because both VPMpc thalamus and the AIGN each have been implicated as functional substrates of CTA learning, the present results suggest that the gustatory thalamocortical relay per se is necessary for normal taste-illness learning.