Large-scale brain network differences during deliberate and spontaneous mind-wandering in a sustained attention task: An electroencephalography source-level connectivity study

Mind-wandering (MW), the shift of attention away from an ongoing task, can be classified as either deliberate or spontaneous, depending on whether these internal thoughts arise intentionally or unintentionally. Previous functional magnetic resonance imaging-based resting state studies have shown that spontaneous MW traits are positively correlated with coupling within the default mode network (DMN), whereas deliberate MW traits are positively correlated with coupling both within the DMN and between the DMN and control-or attention-related networks. However, state-based functional connectivity during each MW episode remains unknown. Addressing this knowledge gap, we investigated how deliberate and spontaneous MW differentially involve state-based large-scale network interactions during a sustained attention task using electroencephalography (EEG), which captures rapid network dynamics. Thirty-one participants performed the gradual-onset continuous performance task using 64-channel EEG. Mental states were classified via experience-sampling probes as on-task, deliberate, or spontaneous MW. EEG data from 1-s pre-probe epochs were analyzed using source estimation and the weighted phase lag index to assess functional connectivity within and across the DMN, control network (CN), dorsal attention network (DAN), and salience network (SN) in the delta, theta, alpha, and beta frequency bands. Relative to both spontaneous MW and the on-task state, deliberate MW was characterized by significantly stronger alpha band functional connectivity. A prominent connectivity cluster was centered on the right frontal operculum-insula of the SN, linking regions across the SN, CN, and DMN. In addition, deliberate MW exhibited enhanced SN-DAN-DMN coupling compared with the on-task state. By contrast, spontaneous MW did not show significant connectivity differences relative to the on-task state in any frequency band. Taken together, these results suggest that alpha band network interactions centered on the SN may contribute to the intentional regulation of internally directed thought during deliberate MW.