Mental-Fatigue-Related Changes in EEG Microstate Dynamics and Microstate-Conditioned Phase-Amplitude Coupling

Mental fatigue in pilots is a critical risk factor for flight safety. This study aimed to characterize electroencephalographic (EEG) microstate temporal dynamics and microstate-conditioned phase-amplitude coupling across different levels of mental fatigue during a simulated-flight task, and to examine the within-participant associations between these measures.

EEG signals were acquired during simulated-flight tasks to analyze neural activity patterns across different mental fatigue levels. The study focused on the temporal parameters of EEG microstates, and the theta-low-beta, theta-high-beta, alpha-low-beta, and alpha-high-beta phase-amplitude couplings (PACs) in the frontal and parietal lobe regions. Linear mixed-effects models were employed to analyze how microstate parameters and PAC metrics varied with mental fatigue levels. Repeated-measures correlations examined within-participant associations between microstate C temporal parameters and PAC under low and high mental fatigue.

Compared with the low mental fatigue condition, high mental fatigue was associated with shorter duration, lower occurrence, and lower time coverage of microstate C. Within microstate C, high mental fatigue was associated with higher theta-low-beta PAC in the left parietal and right frontal regions; theta-high-beta PAC in the left frontal, left parietal, and right frontal regions; alpha-low-beta PAC in the bilateral frontal regions; and alpha-high-beta PAC in the right frontal region. Repeated-measures correlations further revealed multiple significant negative within-participant associations between microstate C temporal parameters and microstate C-conditioned PAC under both fatigue conditions. More associations survived FDR correction under high mental fatigue, and most corresponding coefficients were numerically more negative; however, between-condition differences in the correlation coefficients were not formally tested.

These findings characterize mental-fatigue-related changes in microstate temporal dynamics and microstate-conditioned PAC, together with exploratory within-participant associations between these measures, and provide new insights into the neural activity patterns associated with mental fatigue.