Abnormal neural responses to feedback in depressed adolescents.

Depression rates surge in adolescence, particularly among females. Recent findings suggest that depressed adolescents are characterized by hypersensitivity to negative outcomes and blunted responsiveness to rewards. However, our understanding of the pathophysiology and time course of these abnormalities remains limited. Due to their high temporal resolution, event-related potentials (ERPs) provide an ideal probe to investigate these processes. In the present study, healthy (n = 25) and depressed (n = 26) female adolescents (13-18 years) completed a gambling task during 128-channel ERP recording. Time-domain analyses focused on ERPs linked to initial processing of negative versus rewarding outcomes (feedback-related negativity; FRN), and later, elaborative processing (late positive potential; LPP). Additionally, time-frequency analyses were used to decompose the FRN into its two constituent neural signals: loss-related theta and reward-related delta activity, thereby allowing us to separately probe these two putative mechanisms underlying FRN abnormalities in depression. Relative to healthy adolescents, depressed youth showed potentiated FRN (loss versus reward) responses. Time-frequency analyses revealed that this group difference in the FRN was driven by increased loss-related theta activity in depressed youth, and not by reward-related delta activity. For the LPP, healthy adolescents exhibited sustained positivity to rewards versus losses, whereas depressed adolescents showed the opposite pattern. Moreover, an enhanced LPP to losses was associated with rumination. In summary, the LPP may be a sensitive probe of depressive rumination, whereas FRN-linked theta activity may represent a neural marker of hypersensitivity to negative outcomes in depressed youth. Implications for treatment and future ERP research are discussed.