Spatiotemporal electroencephalography microstate analysis in disorders of consciousness

Disorders of consciousness (DOC) are associated with abnormal transitions of brain state. However, studies about brain state have basically focused on large time scale at present. Microstate analysis can depict temporal and spatial dynamics of the brain activity on a small scale. In this study, we aimed to discuss whether microstates were altered in patients with DOC, and if the microstates' temporal properties reflected a link to the patients' clinical features so as to study the pathophysiological mechanisms underlying DOC from the perspective of transitions of brain state. Resting state EEG signals from forty-five subjects, including twenty-seven DOC patients and eighteen healthy controls (HCs) were recorded. Results revealed that four types of microstate topographic maps (A-D) were mapped to DOC group and HC group respectively, in which DOC patients had a unique spatial microstate class C that was different from the HCs. Statistical test results of microstate temporal properties showed that DOC patients had significantly higher occurrence for microstate A and B, and coverage for microstate C and D compared to HC. On the contrary, durations of microstate A, C and D, and coverage of microstate B were significantly decreased in DOC patients. Furthermore, a positive spearman's correlation was found between the duration D and Coma recovery scale-revised (CRS-R) scores. Besides, microstate transition probabilities (except C to A and D to A) showed significant alternations for DOC patients compared to HCs, indicating that the dynamic transition laws of brain states in DOC patients had changed on whole brain scale. These results may deepen our understanding of brain dysfunction caused by DOC and help us to understand the pathological neural mechanisms of DOC.