Altered reward feedback processing in methadone maintenance treatment patients: An ERP study using the monetary incentive delay task.

Opioid use disorder (OUD) is a significant global health challenge marked by neurophysiological abnormalities affecting mood, motivation, memory, and reward processing. While methadone maintenance treatment (MMT) is widely employed to treat OUD, its impact on neural reward mechanisms remains poorly understood. In this study, we investigated the electrophysiological correlates of reward processing in 15 MMT patients and 21 healthy controls using the Monetary Incentive Delay (MID) task combined with electroencephalography (EEG). MMT patients performed the task both before and 30 min after the methadone intake. Event-related potential components, specifically feedback-related negativity (FRN) and feedback P3 (FB-P3), were compared between groups. We found that behavioral performance, including reaction times and accuracy, did not differ significantly between MMT patients and healthy controls across win and loss conditions. However, EEG results revealed that MMT patients showed significantly more negative FRN amplitudes at frontal electrodes compared to HCs under both win-hit and loss-hit conditions, suggesting their deficits in neural processing of reward feedback. No significant differences in FB-P3 amplitudes at central electrodes were observed between groups. Additionally, no significant changes in FRN amplitudes were detected in MMT patients before and after methadone administration. These findings provide preliminary evidence of altered neural processing of reward feedback in individuals receiving stable long-term MMT, and acute methadone administration did not appear to modulate these responses. Further research is needed to clarify the clinical relevance of these neural alterations and their potential role in treatment outcomes.