Context coding in the mouse nucleus accumbens modulates motivationally relevant information

Neural activity in the nucleus accumbens (NAc) is thought to track fundamentally value-centric quantities linked to reward and effort. 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 nonvalue signals are encoded in NAc. We recorded NAc neural ensembles while head-fixed mice performed an odor-based biconditional discrimination task where an initial discrete cue modulated the behavioral significance of a subsequently presented reward-predictive cue. We extracted single-unit and population-level correlates related to the cues and found value-independent coding for the initial, context-setting cue. This context signal occupied a population-level coding space orthogonal to outcome-related representations and was predictive of subsequent behaviorally relevant responses to the reward-predictive cues. Together, these findings support a gating model for how the NAc contributes to behavioral flexibility and provide a novel population-level perspective from which to view NAc computations.

Automated summary

Neural activity in the nucleus accumbens (NAc) is believed to encode fundamental value-centric quantities related to reward and effort. However, the NAc also contributes to flexible behavior that cannot be explained solely by value signals. This study recorded NAc neural ensembles while mice performed an odor-based task and found that nonvalue signals are encoded in the NAc for the initial contextual cue, which predicts subsequent behaviorally relevant responses to reward-predictive cues.