Contextual gating of motivationally-relevant stimuli in the mouse nucleus accumbens

Abstract

Neural activity in the nucleus accumbens (NAc) is thought to track fundamentally value-centric quantities such as current or future expected reward, reward prediction errors, the value of work, opportunity cost, and approach vigor. However, the NAc also contributes to flexible behavior in ways that are difficult to explain based on value signals alone, raising the question of if and how non-value signals are encoded in NAc. We recorded NAc neural ensembles while head-fixed mice performed a biconditional discrimination task where context-setting cues modulated the stimulus-outcome association of subsequently presented reward-predictive cues. We extracted single-unit and population-level correlates of task features, and found value-independent coding for the context cues. This context signal occupied a subspace orthogonal to outcome-predictive representations, and was predictive of subsequent behaviorally-relevant coding. Together, these findings support a circuit-level gating model for how the NAc contributes to behavioral flexibility and provide a novel population-level perspective from which to view NAc computations.