Selective ablations reveal that orbital and lateral prefrontal cortex play different roles in estimating predicted reward value.

Subregions of prefrontal cortex are important for estimating reward values and using these values to guide behavior. The present studies directly tested whether orbital prefrontal cortex (O-PFC) and lateral prefrontal cortex (L-PFC) are necessary for evaluating trial-to-trial changes in the reward values predicted by visual cues. We have compared intact rhesus monkeys, those with bilateral O-PFC lesions (n = 3), and those with bilateral L-PFC lesions (n = 3). We used three versions of a visually cued color discrimination task: we varied reward size, delay to reward, or both. O-PFC lesions altered estimations of predicted reward value in all versions of the task. L-PFC lesions disrupted performance only when both reward size and delay to reward were varied together. Neither lesion directly affected basic internal drive states (satiation curves). Our results suggest that O-PFC is essential for establishing independent, context-specific scales with which predicted reward values are measured. L-PFC appears necessary for integration of predicted reward value across these different scales.