Differential Representation of Motivation and Affective Judgment by Neurons in the Primate Ventral Striatum and Ventral Pallidum during Approach-Avoidance Decision-Making

Decision-making often involves evaluating trade-offs between potential rewards and aversive outcomes, engaging both motivational drive and affective judgment. The ventral striatum (VS) and ventral pallidum (VP) are key regions in these processes. While the VS is associated with reward processing and incentive motivation, the VP encodes hedonic value and mediates motivated behaviors. However, their distinct roles under conditions involving both appetitive and aversive outcomes remain unclear. In this study, we recorded single-unit activity from the VS and VP in macaques performing alternating approach-approach and approach-avoidance tasks. We focused on two behaviorally derived variables: fixation error frequency (FoE), reflecting motivational engagement, and chosen value (ChV), representing subjective value based on cost-benefit evaluation. Results revealed a functional dissociation: VS neurons rapidly adjusted cue-period activity in anticipation of aversive contexts, suggesting their role in modulating internal motivational states. By contrast, VP neurons changed more gradually, except for rapid outcome-locked responses to actual air-puff delivery, indicating their involvement in processing actual aversive events. Nonetheless, neurons in both regions consistently encoded FoE and ChV across tasks. These findings highlight the dynamic yet complementary contributions of the VS and VP to representing motivation and valuation during decision-making under aversive conditions.