Sad expressions during encoding enhance facial identity recognition in visual working memory in depression: Behavioural and electrophysiological evidence

Background: Mood-congruent memory biases are prominently featured in cognitive theories of depression. However, how sad expressions during encoding affect facial identity recognition in visual working memory (WM) and the electrophysiological correlates in depressed individuals are unclear. Methods: Event-related potentials (ERPs) were recorded from 30 depressed participants and 31 controls during a delayed face discrimination task. Results: The depressed participants showed lower discrimination power in facial identity recognition than the controls. However, the depressed participants showed higher discrimination power in facial identity recognition for neutral probe faces preceded by sad expressions than for those preceded by happy expressions, while the controls showed no difference. Furthermore, hits (correctly recognizing studied faces) and associated vertex positive potential (VPP), P3b, and late positive potential (LPP) amplitudes were significantly higher for probe faces preceded by sad expressions than for those preceded by happy expressions in the depressed individuals, whereas the controls showed no differences. No such effects were found for correct rejections (correctly rejecting unstudied faces). Limitations: The present study is limited due to the relatively small sample size and homogenous university population. Conclusions: The findings suggest that for depressed individuals, sad expressions during encoding enhanced discrimination power in facial identity recognition, especially correct recognition of studied faces in visual WM, which was associated with an increase in early structural encoding and more late attentional and perceptual resources following facial identity during retrieval, reflecting a mood-congruent memory bias.