Neurophysiological Pathways of Unconscious Emotion Processing in Depression: Insights From a Simultaneous Electroencephalography-Functional Magnetic Resonance Imaging Measurement

Background: Major depressive disorder (MDD) is characterized by strong emotional dysregulation. Mechanisms driving the negative affect in depression may be fast processes existing on an unconscious level.

Methods: A priming task was conducted using simultaneous electroencephalography-functional magnetic resonance imaging measurement involving presentation of facial expressions (happy, sad, and neutral) to examine the neurophysiological pathway of biased unconscious emotion processing in MDD. Priming prior to a target emotion created unconscious (16.7-ms primer) and conscious (150-ms primer) trials. A large sample (N = 126) was recruited, containing healthy control participants (n = 66; 37 women) and participants with MDD (n = 60; 31 women).

Results: The healthy control group showed a shorter reaction time in happy but not in sad or neutral trials compared with the MDD group. N170 amplitudes were lower in trials with unconscious than conscious primer presentation. N170 amplitudes correlated with cortical (right fusiform gyrus, right middle temporal gyrus, right inferior temporal gyrus, left supplementary motor area, right middle frontal gyrus) and subcortical brain regions (right amygdala). The strength of N170 and brain activity correlation increased when the stimulus was consciously presented. Presented emotions did not affect the correlation of N170 values and brain activity.

Conclusions: Our findings show that MDD may exhibit biased emotion regulation abilities at a behavioral and neurophysiological level. Face-sensitive event-related potentials demonstrate a correlation with heightened brain activity in regions associated with both face recognition (fusiform gyrus) and emotion processing (amygdala). These findings are evident in both MDD and healthy control groups, with lower effect sizes in the MDD group indicating reduced emotion recognition and processing abilities.