Altered microstate dynamics in Functional Neurological Disorder

Background: Functional Neurological Disorder (FND) presents with disabling and heterogeneous motor, sensory, and cognitive symptoms despite the absence of gross structural pathology. A key question is whether symptoms reflect disruptions in the intrinsic organization of brain networks. Electroencephalography (EEG) offers a high temporal resolution view of ongoing dynamics, making it a powerful means to probe such mechanisms. Methods: We applied a seven-class microstate decomposition to resting-state EEG from 39 patients with FND and 47 matched healthy controls to characterize the temporal dynamics of brain activity. Microstate were labelled A-G according to established topographies. Symptom severity was assessed with the Simplified-Functional Movement Disorder Rating Scale, and correlations were tested. Logistic regression was used to assess group discrimination, with accuracy quantified by the area under the curve. Results: Compared to controls, patients with FND exhibit significantly reduced duration of microstate G, associated with sensorimotor integration. This alteration correlated negatively with symptom severity scores and moderately discriminated groups. Transition probabilities analyses uncovered distinct patterns among microstates A, B and C, suggesting both an exaggerated shift from arousal-related to visual imagery networks and resistance to engage in self-referential processing. Conclusions: Our findings provide the first direct evidence of disrupted resting-state microstate organization across a heterogeneous FND cohort.