Catching the drift: EEG microstate dynamics resemble time-on-task changes in mind wandering and sustained attention

Sustained focus is essential for effective goal-directed behavior. Yet, as sustained attention tasks drag on, the occurrence of mind wandering increases. Recent studies suggest that such increases in mind wandering correspond with increases in response time variability and declines in accuracy with greater time-on-task. Relatively little is known about how large-scale brain dynamics unfold over similar timescales. EEG microstates offer a way to characterize these dynamics by capturing brief, quasi-stable topographical patterns that index distinct large-scale neural configurations. Prior work has shown that microstate C corresponds with episodes of mind wandering, whereas microstate E corresponds with task-focused periods. The present study asked whether the prominence of these microstates may systematically shift with greater time-on-task. Thirty-four adults completed a 45-min Sustained Attention to Response Task, while EEG was recorded and canonical microstates were extracted. In line with established behavioral findings, self-reported mind wandering and performance indices suggested poorer task-focus with longer time-on-task. Critically, microstate metrics revealed a gradual increase in the prominence of microstate C (greater time coverage and occurrence) over the course of the task and a corresponding decrease in the prominence of microstate E (shorter duration). These results indicate that EEG microstate dynamics are sensitive to time-on-task related changes in sustained attention and track a shift from externally oriented task focus toward internally oriented, mind wandering states.