Dissociable roles of distinct orbitostriatal circuits in value-based decision-making

About This Grant

7. Project Summary/Abstract We make hundreds of decisions a day. Value-based decision-making requires the orchestration of multiple processes that enable us to learn from prior experience and then use this information to guide our behavior. Deficits in decision-making are common in psychiatric disorders that result from disruptions in how value is estimated or assigned, how value estimates influence action selection, or the ability to make inferences about the environment to guide decisions. These disruptions are unresponsive to current treatments and contribute to the functional disability evident in mental illness. Hence, a deeper understanding of the mechanisms underlying adaptive and maladaptive reward learning is required to address this unmet therapeutic need. Here, we will use fiber photometry, optogenetics, and computational modeling in rats performing two translational behavioral tasks to identify the neurophysiological mechanisms underlying value-based decision-making. The orbitofrontal cortex (OFC) and the striatum are essential mediators of reward processing and decision-making, and both the ventromedial and lateral subregions of the OFC (vmOFC and lOFC, respectively) project glutamatergic neurons to the striatum in a topographic manner; the vmOFC mostly innervates the medial striatum (mS) whereas lOFC preferentially targets central striatal regions (cS). Identifying how these distinct orbito-striatal pathways contribute to specific aspects of value-based decision-making is essential. We aim to (1) identify how dynamic changes in vmOFC→mS and lOFC→cS circuit activity mediate flexible reward learning and (2) determine how alterations in circuit activity disrupt this process. Specific Aim 1 will use dual-color fiber photometry to measure the activity of the vmOFC→mS or lOFC→cS circuits with simultaneous measurement of local OFC parvalbumin-positive (PV+) GABA interneuron activity. Specific Aim 2 will use complementary gain- or loss-of-function optogenetic interventions to confirm the functional relevance of neural activity during behavior. These optogenetic manipulations – targeting orbito-striatal glutamate circuits or OFC PV+ interneurons – will be delivered to (1) enhance the dynamic changes in neural activity associated with optimal task performance or (2) perturb normal neural activity and induce behaviorally distinct disruptions value-based decision-making. Each Specific Aim will evaluate value-based decision-making in rats tested in a probabilistic reversal learning (PRL) or 2-step reinforcement learning task. Computational models of reinforcement learning will provide an in-depth analysis of behavioral performance, and regression analysis will determine how changes in neural activity contribute to task performance. With a multidisciplinary approach and high cell-type- and circuit-specificity, our findings will elucidate the neurobiological mechanisms underlying decision-making and provide critical insight for the development of new and effective therapeutic strategies for mental illness.