Neurophysiological evidence of cognitive inhibition anomalies in persons with major depressive disorder

Objective: The neural correlates of inhibitory deficits for emotional semantic material in persons with major depressive disorder (MDD) were investigated. Methods: Individuals (n = 15) with a diagnosis of MDD or MDD in partial remission, and healthy controls (n = 14) underwent recording of event-related brain potentials (ERPs) while performing a computerized emotional Stroop task. Results: There were no group performance differences on the emotional Stroop task. However, the analysis of ERP waveforms revealed a larger negative wave peaking at about 170 ms over the left than the right hemisphere only in controls; a negative displacement (N450) at parietal sites for positive and negative words only for persons with MDD; in both groups, processing negative and positive words was associated with a positive displacement that peaked at about 450 ms and was larger over the left lateral frontal region; and, the N450 modulation correlated with negative automatic thinking and depressive symptoms. Conclusions: The electrophysiological data reveal early changes in neural activity associated with word processing as well as valence-related changes in the N450 component at parietal sites in MDD. Significance: This valence-related increase in N450 amplitude at parietal sites may reflect an automatic capture of attention by words with emotional valence. (C) 2008 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.