Inferior olive lesions impair concurrent taste aversion learning in rats.

Taste aversion learning can be established according to two different procedures, concurrent and sequential. For the concurrent task, two different taste stimuli are offered at the same time, one associated with simultaneous intragastric administration of an aversive stimulus and the other associated with physiological saline. This discrimination is learned by sham-lesioned control animals and by animals with lesions in the cerebellar cortex but not by rats lesioned in the inferior olive. At the same time, animals with lesions in the inferior olive and sham-lesioned animals achieve sequential learning when the gustatory stimuli are offered individually during each daily session. The results obtained show that electrolytic lesions in the inferior olive impair acquisition of concurrent learning and are analyzed in terms of an anatomical system consisting of the vagus nerve, inferior olive, and cerebellum, which differentiates between the two modalities of taste aversion learning, concurrent and sequential.