AFFECT AND COGNITION IN DEPRESSION: AN RDOC PSYCHOPHYSIOLOGICAL PERSPECTIVE

Efforts to successfully prevent and treat depression might be hindered by an inadequate understanding of its underlying mechanisms. To better understand mechanisms underlying depression and its vulnerability researchers are beginning to examine dimensions of functioning rather than diagnostic categories. This dissertation is a collection of three studies that explored psychophysiological correlates of two promising dimensions, namely the Positive Valence Systems (PVS) and the Negative Valence Systems (NVS), in at-risk individuals (subclinical depression, or dysphoria) and in individuals with clinical depression. In addition, the influence of these two affective symptoms on the Cognitive Systems was explored. Study one explored affective and cognitive processing of pleasant, neutral, and unpleasant images in young adults with dysphoria by examining time- and time-frequency electroencephalographic (EEG) data using a data-driven cluster-based statistical approach. Affective processing was indexed by delta power, while theta power was employed as a correlate of cognitive elaboration of the images. Dysphoria was related to reduced late positive potential (LPP) and delta power to pleasant images relative to controls. Path model analyses showed that the reduced delta power in dysphoria was mediated by anhedonia. Also, dysphoria was characterized by an early increase in theta power for unpleasant images relative to neutral and pleasant ones. Instead, controls were characterized by a late reduction in theta power for unpleasant stimuli relative to neutral and pleasant ones. These results suggest a reduced functioning of the PVS as well as a potential interaction between the NVS and the Cognitive Systems in conferring depression risk. Study two aimed at extending the findings on the PVS in a group of adults with clinical depression. Particularly, the present study aimed at analyzing the LPP and time-frequency delta power in full-blown clinical depression during the viewing of pleasant and neutral pictures. The LPP and delta power to pleasant images were reduced in depression relative to controls. Also, cluster-based statistics revealed greater delta power to pleasant relative to neutral pictures in the control group but not within the depression group. Both a smaller LPP and delta power to pleasant pictures were independently related to depression status. Taken together, Study one and two suggest that reduced time-frequency delta power to pleasant images might be a promising electrocortical correlate of reduced PVS functioning in subclinical and clinical depression. Study three aimed at exploring whether and how the PVS and NVS influence the ability to exert cognitive control in individuals with depressive symptoms. In this study, a non-emotional and emotional task-switching paradigm has been designed to investigate whether individuals with greater depressive symptoms show a general cognitive control difficulty or a specific deficit in affective conditions. Depressive symptoms were characterized by a general difficulty to exert cognitive control (mixed task blocks) in both emotional and non-emotional contexts and by greater difficulty in even simple attentional processing (single task blocks) of emotional material. This study granted novel insights into the extent of Cognitive Systems functioning and the influence of affective dimensions (PVS and NVS). Together, by employing distinct EEG and behavioral measures to tackle several dimensions, these studies extend our knowledge of mechanisms linked to depression and its vulnerability. Ultimately, these findings may contribute to an improved ability to identify and prevent this often chronic and burdensome condition.