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EEG and Cognitive Markers of Reading Disability and Attention-Deficit/Hyperactivity Disorder

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suttorp_hailey_msc_2025_thesis.pdf (1.37 MB)

Date

2025-08-12

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Abstract

ADHD and RD are frequently comorbid in children. What underlies this comorbidity is unclear, but a shared deficit that increases the likelihood of either disorder has been suggested. Processing speed and working memory are commonly implicated. This study addresses the uncertainty by drawing from the HBN biobank with RD (N=101), ADHD (N=533), both ADHD and RD (N=80) and 404 controls. Groups were compared on processing speed, working memory, rapid naming, and executive functioning tasks, as well as resting-state alpha-band EEG. Multinomial logistic regression compared task scores and alpha power difference scores to best predict group membership. The results do not strongly support processing speed or working memory as shared deficits between RD and ADHD. In the comorbid group, the presence of an RD, not ADHD, contributed most to greater impairment across tasks. Resting-state EEG failed to distinguish between groups. Overall, group membership was predicted by both shared and distinct factors.

Summary for Lay Audience

Attention-Deficit/Hyperactivity Disorder (ADHD) and reading difficulties (RD) are common disorders of childhood. ADHD is characterized by inattentional, hyperactive and impulsive symptoms. RD is defined as struggles limited to reading-related skills, that do not extend to other areas of functioning. ADHD and RD often co-occur, as such can contribute to greater challenges for children and adolescents with both disorders. This thesis aimed to better understand what drives the high co-occurrence between RD and ADHD. The study focused on whether challenges in broad cognitive skills, such as processing speed and working memory, increase the likelihood of having ADHD or RD. To investigate this, we compared four groups: ADHD-alone, RD-alone, both ADHD and RD and a control group without either difficulty, across a series of behavioral tests. In addition, to further distinguish groups, we compared brainwave activity during eyes-open and eyes-closed relaxation using a brain-imaging technique called electroencephalography (EEG). The results show no significant differences between the RD-alone and ADHD+RD groups on any of the behavioral tests. In contrast, the ADHD-alone group outperformed the ADHD+RD group across all the behavioural measures. However, brainwave activity during relaxed resting states did not distinguish between groups, although greater activity was found near the back of the head during eyes-closed rest. The groups showed largely common, but not identical cognitive and EEG-related impairments, with varied contributions that increased the likelihood of RD, ADHD, or both. Overall, this research shows that, the addition of an RD, not ADHD, most substantially contributes to greater challenges in the evaluated cognitive skills when ADHD and RD co-occur. Brain activity during eyes-open and eyes-closed relaxation might not be the optimal method to distinguish between these groups. The high co-occurrence of RD and ADHD, however, are most likely due to a combination of common and uncommon weaknesses in broader cognitive skills.

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Keywords

Attention-deficit/hyperactivity disorder (ADHD), Reading Difficulties (RD), comorbid, resting-state, alpha, electroencephalogram (EEG), processing speed, working memory, domain-general

URI

https://hdl.handle.net/20.500.14721/38758

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