Prediction of immediate and future rewards differentially recruits cortico-basal ganglia loops

Abstract

Evaluation of both immediate and future outcomes of an action is a critical requirement for intelligent behavior. We investigated brain mechanisms for reward prediction at different time scales in an fMRI experiment using a Markov decision task. When subjects learned actions from immediate rewards, significant activity was found in the lateral orbitofrontal cortex and the striatum. When subjects learned to acquire large future rewards despite small immediate losses, the dorsolateral prefrontal cortex, inferior parietal cortex, dorsal raphe nucleus, and cerebellum were also activated. Computational model-based regression analysis using the predicted future rewards and prediction errors estimated from subjects’ performance data revealed graded maps of time scale within the insula and the striatum, where ventroanterior parts were responsible for predicting immediate rewards and dorsoposterior parts for future rewards. These results suggest differential involvement of the cortico-basal ganglia loops in reward prediction at different time scales.