UC Berkeley

Attention Deficit/Hyperactivity Disorder (ADHD) is a neurodevelopmental disorder historically considered to be a condition of childhood, characterized by deficits in sustained attention abilities. However, more recent literature has not only begun to reveal it as a lifespan disorder persisting well into adulthood but has also increasingly focused on enhanced distractibility (as opposed to an attention deficit per se) as a core feature. Despite this proposed framework, unbiased physiological markers of enhanced distractibility do not exist, and relevant symptoms continue to be evaluated by subjective behavioral and cognitive assessments. More specifically, measuring underlying neural correlates of enhanced distractibility (such as difficulty ignoring irrelevant external stimuli or difficulty disengaging from task irrelevant internal thought) remains a key goal to better understand ADHD. Preliminary studies have begun to investigate these processes in children. Yet given current understanding of the maturational changes associated with attentional control across development, investigation into how this presentation differs in adults is warranted. As such, I aimed in this dissertation to examine neural differences in processing of external and internal distraction (internal distraction characterized here as mind wandering) between adults with and without ADHD, using EEG/event-related potentials (ERPs). To this end, 26 adult men and women with and without ADHD completed one 30-minute long three-stimulus auditory oddball task, and one 30-minute long two-stimulus auditory oddball task, while their behavioral and EEG data were recorded. Study participants also completed several questionnaires probing mood and attention in daily life. Adults with ADHD showed increased reaction time variability in response to distractor tones as well as a tendency for decreased MMN latency, compared to controls. Additionally, in adults with ADHD, the ERP P3a response to distracting tones was significantly larger in amplitude and significantly shortened in latency than to target tones, a pattern that did not exist for adults without ADHD. Although no neural differences were found during periods of on task versus internally distracted thought, adults with ADHD showed a trend to slowing in response time during periods of mind wandering. Additionally adults with ADHD reported more frequent engagement in unintentional mind wandering and reported being significantly more impaired by mind wandering in daily life than adults without ADHD. Overall, these findings contribute to a growing literature examining enhanced distractibility as a key feature of ADHD, providing initial insight into external and internal distraction processes in adults with ADHD. These preliminary results suggest that adults with ADHD may indeed be more “captured” than adults without ADHD by both external and internal distraction. Future work should consider examining the utility of measures of enhanced distractibility, in addition to impaired sustained attention, in the diagnosis of this condition.