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Séminaire - Shauna ParkesCircuitry underlying instrumental incentive learning and memory

Abstract :

Choice between goal-directed actions is determined by the relative value of their consequences. Such values are encoded during incentive learning and later retrieved to guide performance. The role of the basolateral amygdala (BLA), the gustatory region of the insular cortex (IC) and the nucleus accumbens (NAc) core was assessed in five experiments. Rats were trained on two actions for distinct outcomes after which one of the two outcomes was devalued by specific satiety immediately prior to a choice extinction test. We first showed that, relative to appropriate controls, outcome devaluation recruited both the BLA and the IC but not the NAc core based on activation of the immediate early gene Arc; however, we found that infusion of the NMDAr antagonist ifenprodil into the BLA only abolished outcome devaluation when given prior to devaluation. In contrast ifenprodil infusion into the IC was effective whether made prior to devaluation or test. Next, we assessed whether the BLA and IC interact during incentive learning and retrieval to guide choice. We hypothesized that the BLA encodes and the IC retrieves incentive value for choice and, to test this, developed a novel sequential disconnection procedure. Blocking NMDAr activation unilaterally in the BLA before devaluation and then contralaterally in the IC before test abolished selective devaluation. In contrast, reversing the order of these infusions left devaluation intact. These results confirm that the BLA and IC form a circuit mediating the encoding and retrieval of outcome values, with the BLA encoding and the IC and retrieving such values to guide choice. The final experiment examined the interaction between the nucleus accumbens core and the insular cortex in the retrieval of outcome value and subsequent performance of goal-directed actions.


SHAUNA PARKES | Postdoctoral Research Associate

Shauna Parkes earned her PhD in Behavioural Neuroscience at The University of New South Wales. Her PhD research focused on the role of the basolateral amygdala and NMDA receptors in higher-order conditioned fear under the supervision of Dr Frederic Westbrook. Her research at the Brain & Mind Research Institute in Dr Bernard Balleine s lab investigates the role of the basolateral amygdala and insular cortex in instrumental incentive learning. Specifically, she is establishing the role of local and afferent circuits in encoding outcome value and the role of its efferents in the retrieval of incentive value.