Reduced P300 in depression: Evidence from a flanker task and impact on ERN, CRN, and Pe.

Individuals with current depression show reduced amplitude of the P300 component of the stimulus-locked event-related potential (ERP)-an effect most often examined in oddball tasks. Although imperative stimuli in response-monitoring paradigms (e.g., the flanker task), also elicit a P300, it is unclear whether a blunted P300 can be observed in depression in these tasks. Moreover, the P300 overlaps with the correct-response negativity (CRN) and error-related negativity (ERN), and is similar to the error positivity (Pe)-response-locked ERPs frequently examined in flanker tasks. The current study examined the stimulus-locked P300 and response-monitoring ERPs on error (i.e., ERN, Pe) and correct responses (i.e., CRN) during an arrowhead flanker task in 72 individuals with a current depressive disorder and 42 never depressed healthy individuals. Consistent with findings from oddball tasks, P300 amplitude was reduced among participants with depression. Further, results indicated increased ERN and CRN, and decreased Pe, in depression. However, when the blunted P300 was included in analyses, group differences in response-monitoring ERPs were no longer evident. Accordingly, P300 amplitudes were correlated negatively with the ERN/CRN and positively with Pe in both groups. A blunted P300 in depression can be observed in speeded response tasks, and can produce apparent increases in ERN and CRN due to ERP component overlap. Further, reduced Pe in participants with depression may reflect a reduced P300 to error commission. These data highlight the central role of reduced P300 in clinical depression, and demonstrate that this effect can be observed across both stimulus- and response-locked ERPs in speeded response tasks.