Frontal cortical effects on feedback processing and reinforcement learning: Relation of EEG asymmetry with the feedback-related negativity and behavior

Reinforcement learning refers to the acquisition of approach or avoidance action tendencies through repeated reward/nonreward feedback. Although much research on reinforcement learning has focused on the striatum, the prefrontal cortex likely modulates this process. Given prior research demonstrating a consistent pattern of lateralized frontal cortical activity in affective responses and approach/avoidance tendencies in the EEG literature, we aimed to elucidate the role of frontal EEG asymmetry in reinforcement learning. Thirty-two participants completed a probabilistic selection task in which they learned to select some targets and avoid others though correct/incorrect feedback. EEG indices of frontal cortical asymmetry were computed from alpha power recorded at baseline and during task completion. We also examined the feedback-related negativity ERP component to assess feedback processing associated with activity in the dorsal anterior cingulate cortex. Results revealed that greater right-lateralized frontal cortical activity during learning was associated with better avoidance learning, but neither left- nor right-sided asymmetry reliably related to approach learning. Results also suggested that left frontal activity may relate to reinforcement feedback processing, as indicated by the feedback-related negativity (FRN). These findings offer preliminary evidence regarding the role of frontal cortical activity in reinforcement learning while integrating classic and contemporary research on lateralized frontal cortical functions.