Access Type

Open Access Dissertation

Date of Award

January 2015

Degree Type

Dissertation

Degree Name

Ph.D.

Department

Psychiatry and Behavioral Neurosciences

First Advisor

Jeffrey A. Stanley

Abstract

Attention-Deficit/Hyperactivity Disorder (ADHD) is a heterogeneous, neurodevelopmental disorder which co-occurs often with Reading Disability (RD). ADHD with and without RD consistently have higher inattentive ratings compared with typically developing controls, with co-occurring ADHD and RD (ADHD/+RD) also demonstrating impaired phonological processing. Accordingly, inattention has been associated with greater phonological impairment, though neither the neural correlates of the co-occurring disorders nor the association are well understood from a functional neuroimaging perspective. The goal was to assess to what extent ADHD/+RD differ from ADHD without RD (ADHD/-RD) and typically developing controls (TDC) in functional activation of attention- and reading-related areas during various tasks. The general hypothesis was that ADHD/+RD would show more extensive alterations in attention-related areas and unique alterations in reading-related areas compared with the other two groups.

The results indicated differences between ADHD/+RD and ADHD/-RD in attention processing; ADHD/-RD showed greater activation of frontoparietal areas for digit and word rhyming continuous performance fMRI tasks. Additionally, though some dysfunction was observed in decoding-related areas in ADHD/+RD relative to TDC, the results showed greater evidence of other cognitive impairments influencing decoding abilities across the ADHD/+RD and ADHD/-RD. Once the groups were re-characterized to reflect relative reading abilities in decoding and word recognition, specific cognitive and functional activation profiles surfaced for three groups: Balanced, Decoders, and Sight Readers.

Two findings contribute to a better understanding of ADHD and RD. First, the functional activation differences between the ADHD subgroups suggest that RD needs to be characterized specifically in ADHD neuroimaging studies and that non-linguistic stimuli should be used to mitigate RD-related confounds in ADHD studies. Second, the role of cognitive impairments, including the level of inattention, on phonology requires clarification from a neuroimaging perspective. Lastly, the novel Reading Tendency Index provides an estimation of an individual's preferred strategy for single word reading without the influence of variable processing speeds. The Index corresponds with predictable neural activations and has implications for instructional and remediation practices.

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