Error processing in major depressive disorder: evidence from event-related potentials.

In a previous study we showed that errors following errors activate a strategic (prefrontal) mechanism. In an error trial (trial n) following an erroneous previous trial (trial n - 1) healthy control subjects were found to have enlarged (more negative) amplitudes of the error related negativity (ERN)/error negativity (Ne), an electrophysiological correlate of response monitoring, in response to a negative feedback signal. Contrary to that, patients with major depressive disorder showed smaller (less negative) ERN/Ne amplitudes. It has been discussed controversially whether errors of choice (e.g., pressing an incorrect response button in an Eriksen flanker task) and errors of commission (e.g., pressing a button when one is not supposed to in a Go/Nogo task) are related to different ERN/Ne mechanisms. In the present study, we examined whether our previous result only holds for errors of choice in an Eriksen flankers task or extends to errors of commission in a Go/Nogo task, as well. Ten patients with DSM-IV major depressive disorder and 10 matched controls participated in a Go/Nogo task with performance feedback which signaled monetary reward. Patients with major depressive disorder again showed a less negative ERN/Ne amplitude in error trials following error trials. This result might reflect impaired response monitoring processes in major depressive disorder resulting from an impaired activation of a central reward pathway and/or a deficit in strategic reasoning.