Dysfunction of processing task-irrelevant emotional faces in primary insomnia patients: an evidence from expression-related visual MMN

Purpose According to the cognitive processing perspectives, patients with insomnia have insufficient neural management of expressional information. In this study, we compared the pre-attentive processing function of task-irrelevant facial expressions in patients with primary insomnia (PI) and matched healthy controls, with expression-related mismatch negativity (EMMN) elicited by emotional faces as the indicator. Methods Using three schematic facial expressions (neutral, happy, and sad) as task-irrelevant stimuli, we investigated the visual processing of PI patients ( n = 22) and healthy subjects ( n = 22) in an expression-related oddball paradigm designed to elicit the visual N170 and EMMN component. After recording and analyzing the electroencephalogram of all participants, amplitude analysis of N170 and EMMN was eventually conducted under corresponding time window. Results Compared with control group, the amplitude of sad-EMMN component was significantly attenuated in patients with PI, while no remarkable difference was observed under the happy condition. In addition, negative cognitive bias was further validated in the control group, but not presented in the PI group. Conclusion The current data suggest dysfunctional expressional information processing in PI patients, accompanied by the disorganization of high level perceptual strategy of processing facial emotional expression.