Dopamine waves as a mechanism for spatiotemporal credit assignment
Arif A. Hamid, Michael J. Frank*, Christopher I. Moore*

Department of Neuroscience, Department of Cognitive Linguistics & Psychological Sciences, 
Carney Institute for Brain Science, Brown University, Providence, RI
* These authors contributed equally to this work; alphabetical order

Abstract
Significant evidence supports the view that dopamine shapes learning by encoding reward prediction errors. However, it is unknown whether striatal targets receive tailored dopamine dynamics based on regional functional specialization. Here, we report novel, wave-like spatiotemporal activity-patterns in dopamine axons and release across the dorsal striatum. These waves switch between activational motifs and organize dopamine transients into localized clusters within functionally related striatal sub-regions. Wave trajectories at rewards were tailored to task demands, propagating from dorsomedial to dorsolateral striatum when outcomes are contingent on animal behavior, and in the opponent direction when rewards are independent of behavioral responses. We propose a computational architecture in which striatal dopamine waves are sculpted by inference about agency, and provide a mechanism to direct credit assignment to specialized striatal subregions. Supporting model predictions, dorsomedial dopamine activity during reward-pursuit signaled the extent of instrumental control, and interacted with reward waves to predict future behavioral adjustments.

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