Impairments of Implicit Emotional Neurocognitive Processing in College Students With Subthreshold Depression: An ERP Study

Purpose: Previous studies have proved that the people with subthreshold depression (SD) had negative cognitive bias in conscious level. However, it still remains a point of controversy whether they have impairment in unconscious level. The present study aimed to explore whether the implicit emotional processing differed between people with SD and healthy controls (HCs) and the details by analyzing the event-related potentials. Methods We recruited 35 SD participants and 35 age- and sex-matched HCs to collect event-related potential data. A visual oddball task was used to investigate implicit emotional processing with three types of emotional pictures (positive, negative, and neutral as stimuli). The N2 and P3 components were used to compare the neurocognitive differences of implicit emotional processing between two groups. Results: Compared with the HC group, the SD participants showed no significant differences in the amplitudes or latencies of the N2 component for any kind of emotional stimuli but smaller P3 amplitudes for all kinds of emotional stimuli. The P3 latencies for positive stimuli were slower than the negative ones in the SD group but not in the HC group. The SD group showed slower P3 latencies than the HC group only for positive stimuli. There was a positive correlation between Center for Epidemiological Survey, Depression Scale score and average N2 and P3 amplitudes. Conclusions: The SD people demonstrate implicit cognitive processing impairments, and the impairments of emotional cognitive processing in SD may exist mainly in evaluative stage and primarily for positive stimuli.