Neurophysiological indices of error monitoring in schizophrenia and major depressive disorder

Error processing anomalies have been implicated in the etiology and maintenance of major depressive disorder (MDD) and schizophrenia. The current work comprised three studies exploring two general aims. Aim 1 used event-related brain potential (ERP) methods to delineate the stages at which error monitoring may be impaired in major depressive disorder and schizophrenia. Aim 2 examined the susceptibility of these respective anomalies to modulation by motivation and emotion. These aims were pursued in three studies that elicited error monitoring under conditions in which motivation (Studies 1 and 2) and emotion (Study 3) were salient for individuals with schizophrenia or major depression. In Studies 1 and 2, healthy controls and individuals with schizophrenia (Study 1) or MDD (Study 2) performed a flanker task under two external motivation conditions (i.e., monetary reward for correct responses and monetary loss for incorrect responses) as well as a non-monetary condition. In Study 3, participants with and without schizophrenia performed an affective flanker task in which the presentation of neutral, positive, or negative distractor images was followed by emotionally congruent or incongruent target faces. In all studies, the error-related negativity (ERN) of the ERP on error-trials assessed the degree to which anomalies in automatic error-detection exist; error-positivity (Pe) was used to quantify subjective recognition of errors; and the P300 of the event-related brain potential indexed the salience of performance feedback. In addition, the late-positive potential (LPP) of the ERP assessed the degree of engagement to affective stimuli in Study 3. The primary conclusions drawn from this work are that: (a) individuals with schizophrenia exhibit deficits in internal feedback signals regarding errors (diminished Pe) and enhanced sensitivity to external performance feedback (enhanced P300); (b) individuals with MDD show excessive sensitivity at initial error detection stages (enhanced ERN); and (c) in individuals with schizophrenia, neural engagement with negative affective stimuli (enhanced LPP) predicts impairments in both behavioral and neural indices of error monitoring as indicated by decreased accuracy and diminished ERN magnitude. Together, these data indicate specific differential deficits in schizophrenia and major depression; results are discussed with regard to current clinical, biological, and cognitive understandings of the disorders.