Neural correlates of negative emotion processing in subthreshold depression.

Subthreshold depression (SD) is regarded as a major risk factor for major depression. However, little is known about the neural mechanism of negative emotion processing in SD. The study aimed to examine the different neural correlates for negative emotion processing in SD and health controls (HCs) and to investigate changes in functional connectivity in SD compared with HC. Blood oxygenation level-dependent (BOLD) responses of SD and HC were captured while performing a passive viewing task, which comprised a negative condition and a masked condition. A total of 42 SD and 32 HC adolescents participated in the study. Between-group comparisons revealed significant reduced activations in the superior frontal gyrus (SFG), middle frontal gyrus and middle cingulate gyrus. Region of interest (ROI) analyses did not find correlations between contrast values of the ROIs and depressive symptoms. In addition, we found a significant increased functional connectivity between the SFG and caudate, pallidum and insula, which was significantly correlated with depressive symptoms in the SD group (P < 0.05). Altered functional connectivity between the SFG and caudate, pallidum and insula may underlie the pathology of SD. This is the first study to investigate neural mechanisms of negative emotion processing in SD using task-based functional magnetic resonance imaging.