THE EARLY POSTERIOR NEGATIVITY (EPN) IS SENSITIVE TO EMOTION STIMULI AND COGNITIVE BIAS TRAINING IN PATIENTS WITH MAJOR DEPRESSION AND CONTROLS

Major depressive disorder (MDD) is accompanied by biased information processing, not only with regard to negative, but also to positive valence stimuli. Here we assessed a tablet based cognitive bias training (CBM) in MDD and controls using on a dot probe task implicitly directing attention to 100% (experiment condition) or random 50% (control condition) positive stimuli. Before and after training we assessed the early posterior negativity (EPN) derived from EEG in an emotion processing task. We analyzed 100 MDD patients and 101 healthy controls. Subjects saw emotion stimuli with low and high arousal and positive and negative valence stimuli from the International Affective Picture System. Arousal and affective valence ratings were comparable across the four emotion conditions. EPN was derived from occipital electrode positions in the time range of 220ms to 280ms post stimulus onset with higher EPN indicating more negative mean amplitudes.
EPN to emotion stimuli decreased over time but increased with positive valence and high arousal to a comparable degree. The latter interacted with higher EPN to high arousal positive stimuli. A three- way interaction of group, time and training indicated a differential effect of the positivity training in MDD patients. Our data demonstrate emotion and valence to affect EPN with more negative amplitudes to positive and to high arousal stimuli. The EPN may therefore serve as an early cortical indicator of positive valence processing. Differential effects of positive CBM on EPN demonstrate its relevance for treatment of patients with MDD.