Temporally dissociable contributions of human medial prefrontal subregions to reward-guided learning

Abstract

In decision making, dorsal and ventral medial prefrontal cortex show a sensitivity to key decision variables, such as reward prediction errors. It is unclear whether these signals reflect parallel processing of a common synchronous input to both regions, for example from mesocortical dopamine, or separate and consecutive stages in reward processing. These two perspectivesmakedistinct predictions about the relative timing of feedback-related activity in each of these regions, a question we address here. To reconstruct the unique temporal contribution of dorsomedial (dmPFC) and ventromedial prefrontal cortex (vmPFC) to simultaneously measured EEG activity in human subjects, we developed a novel trialwise fMRI-informed EEG analysis that allows dissociating correlated and overlapping sources. We show that vmPFC uniquely contributes a sustained activation profile shortly after outcome presentation, whereas dmPFC contributes a later and more peaked activation pattern. This temporal dissociation is expressed mainly in the alpha band for a vmPFC signal, which contrasts with a theta based dmPFC signal. Thus, our data show reward-related vmPFC and dmPFC responses have distinct time courses and unique spectral profiles, findings that support distinct functional roles in a reward-processing network.