Pure correlates of exploration and exploitation in the human brain
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Balancing exploration and exploitation is a fundamental problem in reinforcement learning. Previous neuroimaging studies of the exploration–exploitation dilemma could not completely disentangle these two processes, making it difficult to unambiguously identify their neural signatures. We overcome this problem using a task in which subjects can either observe (pure exploration) or bet (pure exploitation). Insula and dorsal anterior cingulate cortex showed significantly greater activity on observe trials compared to bet trials, suggesting that these regions play a role in driving exploration. A model-based analysis of task performance suggested that subjects chose to observe until a critical evidence threshold was reached. We observed a neural signature of this evidence accumulation process in the ventromedial prefrontal cortex. These findings support theories positing an important role for anterior cingulate cortex in exploration, while also providing a new perspective on the roles of insula and ventromedial prefrontal cortex.
Keywordsreinforcement learning fMRI decision making
We are grateful to Joel Voss for helpful comments on an earlier draft. This research was carried out at the Harvard Center for Brain Science with the support of the Pershing Square Fund for Research on the Foundations of Human Behavior. This work involved the use of instrumentation supported by the NIH Shared Instrumentation Grant Program, Grant No. S10OD020039. We acknowledge the University of Minnesota Center for Magnetic Resonance Research for use of the multiband-EPI pulse sequences.
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Conflict of interest
The authors declare no competing financial interests.
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