Brain signal complexity tracks mind-wandering and visual perceptual learning.

Often characterized as thoughts unrelated to the ongoing task, mind-wandering occupies up to 50% of our waking hours and impacts neural and behavioural functioning. Until now, research has focused on the impact of mind-wandering on immediate task performance, but its relationship to neural states that support learning-related gains over time remains unclear. Previous research examining brain signal complexity during task performance showed that periods of mind-wandering were associated with higher signal complexity compared with on-task states, reflecting increased neural flexibility. The primary aim of this study was to investigate whether higher signal complexity associated with mind-wandering may represent a flexible neural state conducive to longer-term learning. Twenty-six adults underwent electroencephalography recording while performing a visual texture discrimination task before and after a training period, with their attention state probed throughout the task. Task performance improved and N1 and P3 event-related potential (ERP) amplitudes were modulated significantly following training (p's < 0.01). Moreover, greater pre- and post-training mind-wandering, better post-training performance, and larger ERP amplitudes were all associated with higher signal complexity (p's < 0.05). Overall, these results suggest that greater engagement in mind-wandering is linked to a high-flexibility brain state that supports longer-term learning in low-level perceptual tasks.