Characterizing consciousness states: EEG microstate dynamics in patients with disorders of consciousness during naturalistic movie-viewing.

Consciousness assessment in disorders of consciousness (DoC) patients remains clinically challenging. Dynamic brain activities responsive to sensory stimulations have been suggested to contain consciousness-related information. However, primary sensory processing can occur unconsciously, necessitating evaluation of residual higher-order cognitive functions for effective assessment. In this study, we introduced a movie-viewing paradigm incorporating a scrambled version to control for primary sensory processing and applied electroencephalography (EEG) microstate analysis to capture higher-order neural dynamics. By comparing 23 DoC patients with 23 healthy individuals and 12 conscious brain-injured patients, we found significant abnormalities in microstate D in DoC patients. Healthy individuals and conscious brain-injured patients showed enhanced D-related parameters during intact movie-viewing compared to the scrambled condition. Conversely, DoC patients displayed a significant decrease in Duration, Coverage, Occurrence, and Transition Probabilities of microstate D during intact movie-viewing. Additionally, K-nearest neighbors classifier showed that the differences in microstate features between the intact and scrambled movie-viewing yielded the best classification outcome (AUC = 0.83), in which microstate D parameters serve as the most important features. Our results suggested that EEG microstates during naturalistic movie-viewing, especially microstate D, have the potential to serve as a novel, objective indicator for characterizing and diagnosing the state of consciousness.