EEG microstates during resting-state and dissociative events in patients with psychogenic non-epileptic seizures

Objective: Previous neuroimaging studies indicate complex network alterations in psychogenic non-epileptic seizures (PNES) patients, but brain activity modifications occurring during PNES remain unexplored. This study aimed to analyze EEG microstate metrics in PNES patients both during events and resting state to investigate the neurophysiological changes underlying these dissociative events. Methods: We recruited 22 PNES patients and 24 age- and sex-matched healthy controls. Inclusion criteria included a history of PNES and at least one recorded akinetic PNES during video-EEG. Results: A two-way repeated-measures ANOVA revealed significant class*condition interactions for microstate duration (p = 0.017), coverage (p = 0.012), and global field power (GFP) (p = 0.008). Post-hoc FDR-adjusted paired t-tests showed a significant decrease in microstate C duration (p = 0.036), coverage (p = 0.04), and GFP (p = 0.036) during PNES events compared to resting state. Mann-Whitney U tests showed significantly higher microstate C duration in PNES patients during resting state compared to controls (p = 0.009). Conclusions: Microstate C, previously associated with the default mode network, showed increased duration during resting state and decreased representation during PNES, suggesting a prominent shift in neural activity dynamics within this network during dissociative events. Significance: These findings provide insights into neurophysiological changes occurring during PNES, suggesting an interplay between pathological and adaptive mechanisms in their pathophysiology.