REDUCED ELECTROCORTICAL RESPONSES TO PLEASANT PICTURES IN DEPRESSION: A TIME-DOMAIN AND TIME-FREQUENCY DELTA ANALYSES

The late positive potential (LPP) to pleasant content is an electrocortical indicator of blunted emotional reac- tivity in depression. Additional insight into emotional reactivity can be provided using time- frequency decom- position. The present study examined time- frequency delta in depression and investigated whether the com- bination of time-domain and time-frequency data would explain additional variance in the depression status. The study was a secondary analysis of data collected during a passive viewing task of pleasant and neutral pictures in a community-based sample of 75 participants with a current depressive disorder and 42 controls. A time- frequency analysis on event- related changes within delta frequency band was conducted. Cluster- based statistics revealed a centro-parietal increase in delta power to pleasant relative to neutral pictures in the control group but not within the depression group. Moreover, a fronto- centro-parietal reduction in delta power to pleasant pic- tures emerged in depression relative to controls. Both a smaller LPP and delta power to pleasant pictures were related to depression status. The combination of LPP and delta power explained a greater amount of variance com- pared to the model where LPP was entered as the only predictor of depression status. These data suggest that delta power might be a promising correlate of the hypo- activation of the approach motivational system in depres- sion. A combination of these measures can be leveraged together to enhance clinical utility and to shed light on the underlying mechanisms associated with depression.