A Subregion of Insular Cortex Is Required for Rapid Taste-Visceral Integration and Consequent Conditioned Taste Aversion and Avoidance Expression in Rats.

Postingestive signals are important for shaping appetitive and consummatory responses, but the brain mechanisms required to assimilate interoceptive events with those at the frontlines of ingestion (taste-guided) are poorly understood. Here, we investigated whether an insular cortex (IC) region, which receives viscerosensory input, including gustatory, is required to modify taste-elicited consummatory reactions in response to a real-time interoceptive change using a serial taste reactivity (TR) test where the rats' oromotor and somatic reactions to intraoral (IO) infusions of sucrose were periodically assessed over 45 min following lithium chloride (LiCl) administration. Results showed that neurally-intact rats shifted from an ingestive repertoire to an aversive one as LiCl took effect. Overall, this hedonic shift was delayed in rats with bilateral neurotoxic IC lesions. Rats with greater neuronal loss in posterior gustatory IC displayed fewer aversive reactions to sucrose following this initial LiCl injection. We further assessed whether the failure to integrate interoceptive feedback with ongoing taste-guided behavior impaired acquisition and/or expression of conditioned aversion and/or avoidance in these same rats. Although, as a group, LiCl-injected rats with IC lesions subsequently avoided the sugar in a 48-h two-bottle test, their preference for sucrose was significantly greater than that of the LiCl-injected neurally-intact rats. Overall lesion size, as well as proportion of the posterior gustatory and/or anterior visceral IC were each associated with impaired avoidance. These findings reveal new roles for the posterior gustatory and anterior visceral ICs in multisensory integrative function.