The role of the amygdala-striatal pathway in the acquisition and performance of goal-directed instrumental actions.

The posterior dorsomedial striatum (pDMS) is essential for the acquisition and expression of the specific response-outcome (R-O) associations that underlie goal-directed action. Here we examined the role of a pathway linking the basolateral amygdala (BLA) and pDMS in such goal-directed learning. In Experiment 1, rats received unilateral lesions of the BLA and were implanted with cannula targeting the pDMS in either the ipsilateral (control) or contralateral (disconnection) hemisphere. After initial training, rats received infusions of muscimol to inactivate the pDMS immediately before sessions in which novel R-O associations were introduced. Sensitivity to devaluation by specific satiety was then assessed. Whereas rats in the ipsilateral group used the recently acquired associations to direct performance following devaluation, those in the contralateral group could not, indicating that BLA-pDMS disconnection prevented the acquisition of the new R-O associations. Indeed, evidence suggested that these rats relied instead on learning acquired during prior training to direct performance following devaluation. In Experiment 2, rats underwent similar surgery and training except they received muscimol infusions immediately before devaluation testing. Those in the ipsilateral group showed a selective devaluation effect, again based on the most recently introduced R-O associations. In contrast, rats in the contralateral group showed nonselective performance after devaluation indicating that the BLA-DMS pathway is also required for the expression of selective R-O associations. Together these results suggest that input from the BLA is essential for specific R-O learning by the pDMS.