Unconscious cognitive reappraisal and unconscious expression suppression regulate emotional responses: an ERP study

Expression suppression, a common emotion regulation strategy, involves continuous efforts of the individual to suppress the behavioral expression of their emotional responses. Previous studies on the effect of expression suppression on emotion regulation have reported inconsistent findings. Based on neurophysiological research, the role of expression suppression should be revisited. Therefore, we investigated electroencephalogram (EEG) changes in individuals unconsciously initiating expression suppression while passively observing emotional pictures. We then compared these EEG data with those obtained from individuals engaging in unconscious cognitive reappraisal. Using subjective reporting of emotional experience and event-related potentials (ERPs), i.e., the P1 and late positive potential (LPP), in EEG data, we compared the effects of different emotion regulation strategies on the unconscious emotional responses of 28 college students. Regarding the subjective emotional experience, the reported emotional arousal in the unconscious cognitive reappraisal group and the unconscious expression suppression group was significantly lower than that in the control group, but no significant difference was found between the two groups. The arousal in response to negative pictures was significantly higher than that in response to neutral pictures. Compared with the control group, P1 amplitudes in the parietal and occipital lobes were significantly reduced in the unconscious expression suppression group, and P1 amplitudes in the parietal lobe were significantly decreased in the unconscious expression suppression group. Regarding the LPP amplitude, LPP amplitudes of the unconscious expression suppression group were significantly lower than those of the control group in the three periods, and there was no significant difference with those of the unconscious cognitive reappraisal group in the three periods. The LPP amplitude of the unconscious cognitive reappraisal group was significantly lower than that of the control group at 450-650 ms and 650-800 ms. Therefore, expression suppression occurred slightly earlier than cognitive reappraisal. The P1 latency in the parietal-occipital region of individuals was significantly faster than that in the frontal region. The LPP first manifested in the parietal-occipital region during the 250-800 ms period and expanded to other brain regions over time. The LPP presented differences due to valence at 250-450 ms, but with increased time, the abovementioned differences gradually disappeared. Cognitive reappraisal and expression suppression initiated under unconscious conditions regulated cortical activity in the visual attention and perceptual processing stages. In the early stage of visual attention, unconsciously initiating the two emotion regulation strategies reduced processing of emotional stimuli. In the later stage of perceptual processing, unconsciously initiating the two emotion regulation strategies effectively regulated individuals' perceptual processing of stimuli.