Executive function processes: inhibition, working memory, planning and attention in children and youth with Attention Deficit Hyperactivity Disorder
Wolfe, Monica Eileen
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This study examines the roles of inhibition, attention, working memory, and planning in youth with and without ADHD. As conceptualized in theories of attention, inhibition, and working memory, difficulties with these executive processes interact to manifest in the behavioral syndrome(s) of ADHD. Barkley (1997) proposed disinhibition as the primary deficit of ADHD. Rapport, Chung, Shore, Denney, & Isaacs, (2000) theorized that ADHD results from a primary deficit in working memory. Mirsky (1987) proposed a model of attention which children with ADHD have deficits in abilities to focus/execute, encode and sustain attention. Posner and Petersen (1990) proposed that three attentional networks are responsible for attentional processes and those children with ADHD have deficits in the vigilance network. To investigate the contributions of inhibition, working memory, attention, and planning in executive dysfunction in children with ADHD, measures were selected from factor analytic studies. Children with ADHD-Combined Type demonstrated poorer inhibition and working memory than children with no diagnosis after controlling for IQ effects. No differences in planning and attention were indicated after controlling for IQ effects. However, a predictive discriminant analysis indicated that none of the executive processes contributed to the prediction of group membership. Given correlational and predictive discriminant analysis results, further analyses were conducted to investigate the contribution of the measures selected for the domains. The theoretical model did not represent a good fit of the data. A three-factor model indicated the best representation suggesting that inhibition and attention were not separable. There were no group differences with the revised measurement model for inhibition/attention, working memory and planning. Taken together, results indicated measures originally selected to tap executive function may not be clean measures of inhibition, working memory, planning, or attention processes. In addition, recently proposed theories overlap and conceptualize the multiple constructs involved in ADHD with a variety of methodologies, further contributing to difficulties in interpreting results and measurement issues.