Parabrachial nucleus lesions and conditioned taste aversion: evidence supporting an associative deficit.

Three experiments examined the conditioned taste aversion (CTA) deficit that occurs following electrolytic lesions of the parabrachial nucleus (PBN). In Experiment 1, lesioned rats failed to avoid either a gustatory or an olfactory stimulus that had been paired with lithium chloride-induced toxicosis. In Experiment 2, however, all rats learned a conditioned flavor preference. Finally, in Experiment 3, all controls and 7 of the 12 lesioned rats learned a conditioned place aversion. Together, these results demonstrate that the disruption of CTA in lesioned rats cannot be ascribed to an inability to process either gustatory or visceral afferent information per se. Rather, the data suggest that PBN-lesioned rats are unable to form a specific association between gustatory and visceral cues.