A neural model of proximity to reward

Throughout learning, refinement of cortical activity in cortex, a process termed “credit assignment”, underlies the refinement of behavioral actions leading to reward. While previous research shows striatum’s role in linking behavior to reward, striatum’s role in linking the underlying behaviorally-relevant cortical activity to reward remains unclear. Leveraging a neuroprosthetic task while recording from the rat cortex and striatum, we demonstrate that the striatum encodes the dynamics of the proximity of cortical activity to reward. Such encoding was independent from external task feedback and emerged as cortical activity consolidated over learning, with dorsal and ventral striatum playing complementary yet distinct roles. Striatal activity thus constitutes a neural model of cortical progress towards reward, suggesting one mechanism by which the brain implements credit assignment to refine behavior. ### Competing Interest Statement The authors have declared no competing interest.