Right frontal cortex generates reward-related theta-band oscillatory activity

When participants in a gambling game are given feedback as to whether they won or lost the previous bet, a series of stereotypical brain electrical responses can be observed in the electroencephalogram (EEG) and the stimulus-locked Event-Related Potential (ERP). These include the Feedback-Related Mediofrontal Negativity (FRN), a posterior P300, and a feedback-induced increase in power at the theta (4 to 8 Hz) band over frontal scalp. Although the generators of the FRN and P300 have been studied previously, little is known about the generator of feedback-induced theta. We employed a gambling game in which participants chose either high-risk/high-reward or low-risk/low-reward bets to investigate these feedback-related responses. The FRN was not modulated by the riskiness of the bet, but both P300 and feedback-induced theta were of greater amplitude following high-relative to low-risk bets. Using a bilateral multi-source Beamformer approach, we localized the induced theta-band responses following wins and losses to partially overlapping regions in the right medial frontal cortex, possibly including the Anterior Cingulate. Using a dipole-fitting approach, we found that the generators of feedback-induced theta are anatomically distinct from those of the FRN and P300. (C) 2009 Elsevier Inc. All rights reserved.