Pre-stimulus alpha power during mind-wandering in adults with ADHD.

In neurotypical adults, mind-wandering (MW) is associated with increases in posterior alpha power, reflecting inward-directed mentation, but tonic, cortical arousal remains largely unexplored in adults with attention-deficit/hyperactivity disorder (ADHD), particularly prone to MW. The main aim of this study was to characterize stimulus-independent oscillatory activity during MW and determine how global and spatially localized MW-related cortical arousal differs between ADHD patients and controls. In total, 28 medication-naïve ADHD patients and 28 controls completed a Go/No-Go task, which included thought-probes to detect MW episodes. The electroencephalography (EEG) analysis focused on cortical arousal measures indexed by pre-stimulus alpha power and its variability, using both global scalp-wise analyses and cluster-based permutation approaches. Deliberate and spontaneous MW were associated with distinct spatial patterns of alpha power synchronization, indicating that deliberate (unlike spontaneous) MW maintains relatively active attentional systems. Furthermore, permutation analyses revealed that controls exhibited significantly higher global alpha power without increased variability during MW, consistent with a stable internally oriented attentional state. Patients displayed no alpha power modulations between attentional states and higher alpha power variability during MW, reflecting unstable attentional engagement. These findings highlight dysregulated and variable alpha power dynamics as markers of unstable internal distraction in ADHD.