Frontal brain asymmetry and reward responsiveness: a source-localization study.

The influence of approach and avoidance tendencies on affect, reasoning, and behavior has attracted substantial interest from researchers across various areas of psychology. Currently, frontal electroencephalographic (EEG) asymmetry in favor of left prefrontal regions is assumed to reflect the propensity to respond with approach-related tendencies. To test this hypothesis, we recorded resting EEG in 18 subjects, who separately performed a verbal memory task under three incentive conditions (neutral, reward, and punishment). Using a source-localization technique, we found that higher task-independent alpha2 (10.5-12 Hz) activity within left dorsolateral prefrontal and medial orbitofrontal regions was associated with stronger bias to respond to reward-related cues. Left prefrontal resting activity accounted for 54.8% of the variance in reward bias. These findings not only confirm that frontal EEG asymmetry modulates the propensity to engage in appetitively motivated behavior, but also provide anatomical details about the underlying brain systems.