Michelle Y. Kibby - US grants

[unreadable] DESCRIPTION (provided by applicant): Children with dyslexia frequently present with poor phonological processing and working memory (WM). Furthermore, there is a strong association between their poor phonological processing skills and their inability to store verbal material. Several brain regions have been found to be structurally atypical in dyslexia in MRI studies, and these brain abnormalities have been linked to poor phonological processing. Nonetheless, the relationship between brain structure and WM has received limited attention in the dyslexia literature. Children with ADHD also present with WM deficits. However, the central executive (CE) is primarily affected in ADHD. Hence, there is an interesting dichotomy between the 2 disorders with dyslexia displaying impaired verbal short-term storage and intact CE functioning, and ADHD displaying intact verbal storage but impaired CE functioning. Similar to research on dyslexia, the relationship between WM and brain morphology has received limited attention in the ADHD literature using structural MRI techniques. Thus, the goal of this project is to ascertain the relationship between brain structure and WM functioning in children with dyslexia, ADHD or controls, while determining the extent linguistic processing influences this relationship. Participants will include children with dyslexia, ADHD and controls between the ages of 8-12 years. They will engage in neuropsychological testing of their WM, linguistic functioning, intelligence, and reading ability. Along with cognitive testing, a structural MRI scan will be conducted on each child. Each scan will be analyzed using quantitative structural neuroimaging techniques. Through a correlational design, the relationships between brain morphology, WM and linguistic processing will be examined in children with and without neurodevelopmental disorders. This study will benefit children with dyslexia in terms of providing knowledge that may aid in diagnosis and intervention. For example, through a better understanding of the biological correlates of dyslexia and ADHD, a more rapid diagnosis may be possible than is provided by traditional techniques. Furthermore, earlier diagnosis will allow for earlier placement into intervention, and early intervention has been linked with better treatment outcome than intervention started later. [unreadable] [unreadable] [unreadable]

DESCRIPTION (provided by applicant): Children with dyslexia frequently present with poor phonological processing. However, it is becoming accepted that neurodevelopmental disorders may be best explained by a poly-factorial model which includes other common deficits as well. One such deficit is executive dysfunction. In the 1980s it was recognized that many children with dyslexia have executive dysfunction;however, research into this area largely fell by the wayside when researchers began examining phonological processing more consistently. As a result, much remains unknown about executive dysfunction in dyslexia, especially in terms of how it relates to frontal lobe structure. Dyslexia and ADHD share a high comorbidity, and executive dysfunction is common in children with ADHD. Thus, it is of interest to determine if executive dysfunction and atypical prefrontal structure may be shared contributors between the two disorders. This project will include 100 children, ages 8-12 years: 25 with dyslexia, 25 with ADHD, 25 with comorbid dyslexia/ADHD, and 25 typically developing controls. All subjects will participate in a neuropsychological evaluation of their executive functioning along with a structural MRI scan. Factor analysis will be used to determine latent variables of executive functions. The following frontal regions will be traced: anterior and posterior cingulate, precentral gyrus, orbitofrontal gyrus, mesial frontal cortex, and the superior, middle, and inferior frontal gyri. Using MANCOVA It is hypothesized that children with dyslexia and ADHD will share deficits in fluency, shift, and verbal working memory. ADHD will also have deficits in inhibition and visual working memory. Moreover, it is hypothesized that the right inferior frontal and left orbitofrontal gyri will be smaller in both groups compared to controls. In contrast, the right superior frontal gyrus, mesial frontal cortex, and right anterior cingulate will be smaller in ADHD than dyslexia and controls. When collapsing across prefrontal regions, gray matter will be reduced bilaterally in dyslexia and ADHD, particularly in the right hemisphere. In addition, left prefrontal white matter volume will be reduced in ADHD. This study will benefit children with dyslexia and ADHD by providing knowledge that may aid diagnosis and intervention. For example, by having a better knowledge of the biological correlates of dyslexia and ADHD, a more rapid diagnosis may be possible than is provided by traditional behavioral techniques. Furthermore, earlier diagnosis will allow for earlier placement in intervention, and early intervention is linked with better outcome than treatment started later. PUBLIC HEALTH RELEVANCE: Developmental dyslexia and ADHD are two of the most prevalent childhood disorders. They also have a high rate of co-occurrence. This project will examine executive functioning (various skills/abilities which contribute to goal-directed behavior) and structure of the front aspect of the brain to see if they may be related to both dyslexia and ADHD.