Time course of affective processing bias in major depression: An ERP study

The current study investigated the time course of the affective processing bias in major depressive disorder (MOD) in a visual three-stimulus semantic oddball task using event-related potentials (ERPs). MOD patients showed decreased P1 latency over right posterior regions to negative relative to positive target stimuli, reflecting a very early onset of the negativity bias in emotional perception. Compared to controls, MOD patients showed enlarged anterior P2 amplitude to positive target stimuli, reflecting an affective bias in the early attentional stages of processing. In addition, MDD patients showed relatively high N2 and reduced P3 amplitudes to negative compared with positive target stimuli, as well as marginally reduced N2 amplitude to positive target stimuli compared with controls. This suggests that the negativity bias also occurs during later strategic evaluation stages. Therefore, the present study extended previous findings by demonstrating that the affective processing bias in MDD begins in the early stages of perceptual processing and continues at later cognitive stages. (C) 2010 Elsevier Ireland Ltd. All rights reserved.