Impairments in working memory create difficulties for individuals with ADHD in their academic, social, and occupational activities. The overall hypothesis of this application is that individuals with ADHD engage an altered neural system when performing working memory tasks. This altered system arises as a consequence of an impaired executive system, which is subserved by the anterior cingulate (ACC) and prefrontal cortical regions (PFC). Impaired executive functioning weakens the ability to recruit subsidiary brain regions and strategies that support working memory. Functional imaging techniques give us a window into the neural basis of those strategies. Our imaging data suggest that phonological rehearsal strategies and the brain regions subserving them are impaired in ADHD. Visual-spatial strategies and their associated neural networks, are however, intact. Limited access to both phonological and visual strategies may increase errors and processing speed. We propose the following aims to investigate working memory in children with ADHD: 1) Define the neural correlates of working memory deficits in ADHD children using subtraction techniques in conjunction with a visual serial addition task; 2) Identify the relationship between BOLD signal changes generated during a working memory task and behavior (response time, error type; classroom ratings); and 3) Compare ADHD children with the Combined subtype to Inattentive subtype to identify the working memory neural strategies associated with each. We hypothesize that a general pattern will emerge in which ADHD combined type subjects use a predominantly visual-spatial strategy to perform a working memory serial addition task. The degree of ADHD dysfunction in the natural setting is expected to positively relate to visualspatial activation and negatively to prefrontal cortical activation. We predict that the ADHD-inattentive type will not exhibit the same level of visual-spatial activation during task performance as the Combined-type. Instead they will exhibit reduced activation in the same regions activated by the normal control children. A better understanding of strategies used in ADHD has potential educational implications for how children with ADHD learn and targets for treatment.
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