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 170ms 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 450ms 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.