The effect of tDCS on mind wandering in adults with and without ADHD:

Objective: Individuals with attention deficit- hyperactivity disorder (ADHD) have a higher propensity to mind wandering. The ventromedial prefrontal cortex (vmPFC) and dorsolateral prefrontal cortex (dlPFC), which show reduced functionality in individuals with ADHD, are involved in mind wandering. Methods: Forty adults with or without ADHD received transcranial direct current stimulation (tDCS) in three different conditions including anodal left dlPFC/cathodal right vmPFC stimulation, the reversed montage, and a sham stimulation. During stimulation, in each session, participants performed the sustained attention to response task as a measure of attentional performance, and a task-unrelated thoughts task to monitor mind wandering. Results: A significant main effect of stimulation condition was identified for attentional performance and task-unrelated thoughts. Anodal left dlPFC coupled with cathodal right vmPFC stimulation improved attention task performance and reduced mind wandering. Furthermore, higher baseline mind wandering and ADHD scores independent from the diagnostic group were associated with larger beneficial effects of tDCS on mind wandering. Conclusion: These results described the role of the left dlPFC and the right vmPFC on attentional performance and mind wandering in adults with and without ADHD. tDCS had beneficial effects on mind wandering, and attention with simultaneous anodal left dlPFC and cathodal right vmPFC stimulation, and the size of the effects on mind wandering depended on mind wandering before intervention, and ADHD scores.