Multiple mechanisms for processing reward uncertainty in the primate basal forebrain

The ability to use information about the uncertainty of future outcomes is critical for adaptive behavior in an uncertain world. We show that the basal forebrain (BF) contains at least two distinct neural-coding strategies to support this capacity. The dorsal-lateral BF, including the ventral pallidum (VP), contains reward-sensitive neurons, some of which are selectively suppressed by uncertain-reward predictions (U ^). In contrast, the medial BF (mBF) contains reward-sensitive neurons, some of which are selectively enhanced (U ⁺) by uncertain-reward predictions. In a two-alternative choice-task, U ^ neurons were selectively suppressed while monkeys chose uncertain options over certain options. During the same choice-epoch, U ⁺ neurons signaled the subjective reward value of the choice options. Additionally, after the choice was reported, U ⁺ neurons signaled reward uncertainty until the choice outcome. We suggest that uncertainty-related suppression of VP may participate in the mediation of uncertainty-seeking actions, whereas uncertainty-related enhancement of the mBF may direct cognitive resources to monitor and learn from uncertain-outcomes.