Major Depressive Disorder (MDD) patients exhibit difficulty in forgetting negative material, which may result from specific impairments in memory and attention. However, the underlying neural correlates of the corresponding cognitive deficit have not been elucidated. The present study investigated the electrophysiological characteristics and differences, using event-related potentials (ERPs), between MDD patients and healthy controls (HCs) in an emotional directed forgetting task (EDF) with negative and neutral images.

A total of 26 MDD patients and 28 HCs were recruited for the current study, all of whom were clinically evaluated using the Hamilton Depression Scale. All participants were subjected to ERP measurements during the EDF task, and behavioral data and ERP components were analyzed.

HCs had higher hit rates than did MDD patients; more false alarms occurred in MDD patients than in HCs, and higher false alarm rates occurred with negative images than with neutral images. The reaction times were also longer for MDD patients than for HCs. Larger image-evoked P2 amplitudes and smaller image-evoked N2 amplitudes occurred in MDD patients, whereas they had higher image-evoked late positive potential (LPP) amplitudes both in negative and neutral emotional conditions than the HCs. MDD patients had higher cue-evoked N2 amplitudes and lower cue-evoked P3 amplitudes, elicited by the Remember cue, than the HCs. The Hamilton Depression Rating Scale (24-item edition) scores were positively correlated with the LPP amplitudes that were evoked by negative images in a central location.

Based on these results, we concluded that poor attentional recruiting and allocation, memory inhibitory deficits, and difficulties in memory retention may contribute to the poor performance in the EDF task in MDD patients. The observed ERP patterns provide valuable insights into the neural mechanisms underlying the EDF task in MDD and underscore the potential of EDF as an assessment tool for cognitive and emotional dysregulation in MDD.