Contribution of rat insular cortex to stimulus-guided action

Abstract

Anticipating rewards is fundamental for decision-making. Animals often use cues to assess reward availability and to make predictions about future outcomes. The gustatory region of the insular cortex (IC), the so-called gustatory cortex, has a well-established role in the representation of predictive cues, such that IC neurons encode both a general form of outcome expectation as well as anticipatory outcome-specific knowledge. Here, we used Pavlovian-instrumental transfer (PIT) in male rats to assess if the IC is also required for predictive cues to exert both a general and specific influence over instrumental actions. Chemogenetic inhibition of IC abolished the ability of a reward-predictive stimulus to energize instrumental responding for reward. This deficit in general transfer was evident whether the same or different outcomes were used in the Pavlovian and instrumental conditioning phases. We observed a similar deficit in specific PIT, such that rats with IC inhibition failed to use a reward-predictive stimulus to guide choice toward actions that deliver the same food reward. Finally, we show that rats with IC inhibition also fail to show outcome-selective reinstatement. Together, these data suggest a crucial role for IC in the representation of appetitive outcomes, and particularly in using this representation to guide instrumental action. SIGNIFICANCE STATEMENTAnimals frequently use cues to infer the availability of rewards and to make predictions about future outcomes. The influence of these predictive cues on behaviour can be studied using Pavlovian-instrumental transfer (PIT), in which Pavlovian outcome expectancies can elevate (general PIT) or selectively guide (specific PIT) instrumental actions. In the current study, we show that chemogenetic inhibition of the gustatory region of insular cortex (IC) abolishes both general and specific transfer, as well as the selectivity of outcome-induced reinstatement. These results demonstrate a critical role for the IC in the representation of appetitive outcomes and significantly contribute to a broader understanding of the cortical bases of PIT.