State-dependent alternations of implicit emotional dominance during binocular rivalry in subthreshold depression

Abstract Background: Binocular rivalry, a phenomenon that individuals often experience back-and-forth perceptual alterations when two distinct monocular stimuli are presented to each eye simultaneously, has been reported as a biomarker in several psychiatric disorders. It is unclear whether abnormalities of binocular rivalry in depression could exist when emotional rivaling stimuli are used, and if so, whether the emotional binocular rivalry test could provide a trait-dependent biomarker or a state-dependent biomarker.Methods: Thirty-four individuals with subthreshold depression and thirty-one non-depressed individuals were recruited to perform a binocular rivalry task including implicit emotional processing. The participants were required to report their perceived orientations of the rival gratings in the foreground and simultaneously to neglect emotional face stimuli in the background. The participants were retested after an approximately 4-month time interval.Results: Compared to the non-depressed group, the depressive group showed significantly stronger implicit emotional dominance at the initial assessment. However, the abnormality was not observed at the follow-up assessment. More importantly, individuals displaying stronger emotional dominance at the initial assessment were more difficult for improvement in depressive severity at the follow-up assessment. No difference was found regarding the switching rate between the depressive group and the non-depressed controls.Conclusions: The abnormality on emotional dominance for individuals with subthreshold depression is associated with depressive symptoms over time. The current emotional binocular rivalry test may provide an objective state-dependent biomarker for distinguishing depressive individuals from healthy individuals.