Event-related brain dynamics during mind wandering in attention-deficit/hyperactivity disorder: An experience-sampling approach

Abstract

Adults with attention-deficit/hyperactivity disorder (ADHD) report increased spontaneous mind wandering (MW) compared to control adults. Since MW is associated with ADHD severity and functional impairment, elucidating the brain mechanisms underlying MW may inform new interventions targeting MW and point to neural markers to monitor their efficacy. Population-based electroencephalographic (EEG) studies suggest that weaker event-related decreases in occipital alpha power characterise periods of MW, but no study has examined event-related brain oscillations during MW in individuals with ADHD. Using an experience-sampling method, we compared adults with ADHD (N = 23) and controls (N = 25) on event-related EEG measures of power modulations and phase consistency during two tasks with high and low demands on working memory and sustained attention, and during periods of MW and task focus. Compared to controls, individuals with ADHD showed weaker alpha power decreases during high working memory demands and across sustained attention demands, weaker theta power increases and phase consistency across working memory demands and during low sustained attention demands, and weaker beta power decreases during low working memory demands. These EEG patterns suggest broadly deficient attentional and motor response processes in ADHD. During MW episodes, adults with ADHD showed weaker alpha power decreases in the sustained attention task and lower theta phase consistency in the working memory task compared to controls. These findings suggest that atypical EEG patterns thought to reflect reduced inhibition of task-irrelevant processes and inconsistent stimulus processing underlie increased MW in adults with ADHD and may be useful for future real-time monitoring of treatment effects.

Keywords: ADHD; Adult; Brain oscillations; EEG; Mind wandering; Sustained attention; Working memory.

Fig. 1

Event-related modulations during each task condition (0-back, 1-back) of the Mind Wandering Task (MWT) in the ADHD and control groups. Black boxes indicate significant group differences. The same scale limits are used across each time–frequency plot (A, B, C, D) and the corresponding topographic maps (E, F, G, H). A: Alpha (8–14 Hz) event-related perturbation (ERSP) at parieto-occipital regions. B: Beta (14–30 Hz) ERSP at centro-parietal regions. C: Theta (3–7 Hz) ERSP at fronto-central regions. D: Theta (3–7 Hz) inter-trial phase coherence (ITC) at fronto-central regions. E: Topographic maps for alpha ERSP in the 0–1000 ms window. F: Topographic maps for alpha ERSP in the 0–1000 ms window. G: Topographic maps for theta ERSP in the 0–500 ms window. H: Topographic maps for theta ITC in the 0–500 ms window.

Fig. 2

Event-related modulations during each delay (1 s, 2 s, 5 s, 8 s) of the Sustained Attention Task (SAT) in the ADHD and control groups. Black boxes indicate significant group differences. The same scale limits are used across each time–frequency plot (A, B) and the corresponding topographic maps (C, D, E). A: Alpha (8–14 Hz) event-related perturbation (ERSP) at parieto-occipital regions. B: Theta (3–7 Hz) and beta (14–30 Hz) ERSP at centro-parietal regions. C: Topographic maps for alpha ERSP in the 0–1000 ms window. D: Topographic maps for theta ERSP in the 0–500 ms window. E: Topographic maps for beta ERSP in the 750–1500 ms window. Note: topographic maps are not shown for the 1 s delay condition as beta increase was not measured in this condition due to the shorter inter-stimulus interval.

Fig. 3

Event-related modulations during task focus and mind wandering (MW) in the mind wandering task (MWT) in the ADHD and control groups. Black boxes indicate significant group differences. The same scale limits are used across each time–frequency plot (A, B, C) and the corresponding topographic maps (D, E, F). A: Alpha (8–14 Hz) event-related spectral perturbation (ERSP) at occipital-parietal regions. B: Theta (3–7 Hz) ERSP at fronto-central regions. C: Theta (3–7 Hz) inter-trial phase coherence (ITC) at fronto-central regions. D: Topographic maps in the 0–1000 ms window for alpha ERSP. E: Topographic maps in the 0–500 ms window for theta ERSP. F: Topographic maps in the 0–500 ms window for theta ITC.

Fig. 4

Event-related modulations during task focus and mind wandering (MW) in the sustained attention task (SAT) in the ADHD and control groups. The same scale limits are used across each time–frequency plot (A, B, C) and the corresponding topographic maps (D, E, F). A: Alpha (8–14 Hz) event-related spectral perturbation (ERSP) at occipital-parietal regions. B: Theta (3–7 Hz) ERSP at fronto-central regions. C: Theta (3–7 Hz) inter-trial phase coherence (ITC) at fronto-central regions. D: Topographic maps in the 0–1000 ms window for alpha ERSP. E: Topographic maps in the 0–500 ms window for theta ERSP. F: Topographic maps in the 0–500 ms window for theta ITC.