PT  - JOURNAL ARTICLE
AU  - Momchil S. Tomov
AU  - Van Q. Truong
AU  - Rohan A. Hundia
AU  - Samuel J. Gershman
TI  - Dissociable Neural Correlates of Uncertainty Underlie Different Exploration Strategies
AID  - 10.1101/478131
DP  - 2019 Jan 01
TA  - bioRxiv
PG  - 478131
4099  - http://biorxiv.org/content/early/2019/12/19/478131.short
4100  - http://biorxiv.org/content/early/2019/12/19/478131.full
AB  - Most real-world decisions involve a delicate balance between exploring unfamiliar alternatives and committing to the best known option. Uncertainty lies at the core of this “explore-exploit” dilemma, for if all options were perfectly known, there would be no need to explore. Yet despite the prominent role of uncertainty-guided exploration in decision making, evidence for its neural implementation is still sparse. We investigated this question with model-based fMRI (n = 31) using a two-armed bandit task that independently manipulates two forms of uncertainty underlying different exploration strategies. The relative uncertainty between the two options was correlated with BOLD activity in right rostrolateral prefrontal cortex and drove directed exploration, a strategy that adds an uncertainty bonus to each option. The total uncertainty across the two options was correlated with activity in right dorsolateral prefrontal cortex and drove random exploration, a strategy that increases choice stochasticity in proportion to total uncertainty. The subjective estimates of uncertainty from both regions were predictive of subject choices. Finally, the decision value signal combining relative and total uncertainty to compute choice was reflected in motor cortex activity. The variance of this decision value signal scaled with total uncertainty, consistent with a sampling mechanism for random exploration. Overall, these results are consistent with a hybrid computational architecture in which different uncertainty computations are performed separately and then combined by downstream decision circuits to compute choice.