Neuronal mechanisms in prefrontal cortex underlying adaptive choice behavior.

This chapter aims to address two questions relating to the role of the prefrontal cortex (PFC) in reward-guided choice behavior. First, do PFC neurons encode rewards per se, or are they encoding behavioral sequelae of reward? To address this, we recorded simultaneously from multiple PFC subregions, with the rationale that neuronal selectivity that directly encoded the reward outcome should occur before selectivity that reflected reward-related sequelae. Our results indicate that neurons in the orbitofrontal cortex (OFC) encode reward information before neurons in the dorsolateral PFC (DLPFC). Furthermore, whereas DLPFC neurons encoded both the upcoming response as well as the expected reward, OFC neurons encoded the reward alone. Our interpretation of these results is that the OFC encodes the reward and passes this information to the DLPFC, which uses it to determine the behavioral response. The second question is whether the encoding is specific to the reward outcome or reflective of a more abstract value signal that could facilitate decision making. We examined this by determining whether the PFC encodes other types of information relevant to decision making, such as probability of success and effort. We found that many PFC neurons encoded at least one of these variables, but neurons in the OFC and the medial PFC (MPFC) encoded combinations of the variables indicative of encoding an abstract value signal. This signal could provide decision making with flexibility and a capacity to deal with novelty, which are two of the hallmark features of prefrontal function. Future research will focus on delineating the differential contributions of the OFC and the MPFC to decision making.