Pre-training inactivation of basolateral amygdala and mediodorsal thalamus, but not orbitofrontal cortex or prelimbic cortex, impairs devaluation in a multiple-response/multiple-reinforcer cued operant task

Abstract

Reinforcer devaluation is a task often used to model flexible goal-directed behavior. Here, we inactivated basolateral amygdala (BLA), orbitofrontal cortex (OFC), mediodorsal thalamus (MD) (Exp. 1) and prelimbic cortex (PL) (Exp. 3) in rats during multiple-response/multiple-reinforcer operant training with levers available to earn reinforcers during cued trials. After two training days with each lever-food relationship, a reinforcer was devalued through selective satiety and devaluation was assessed in a choice test with the brain areas non-inactivated. The control and OFC and PL inactivation groups exhibited a devaluation effect, but the BLA or MD groups did not. Since the OFC is proposed to be required in devaluation tasks when a discrete cue signals an outcome and PL is proposed to be required when responses based on lever spatial-location guide behavior, we ran new rats through a cue-switching experiment (Exp. 2) to determine the strategy rats use to complete our task (attending to the discrete light cue or spatial lever location). Both groups (cue switched and cue normal) showed a devaluation effect based on the lever spatial location, suggesting that rats rely on the spatial lever location to guide behavior. Future studies will determine whether OFC and PL can compensate for each other to show intact devaluation when the functioning of one of them is impaired.