Analysis of specific attentional functions in attention-deficit/hyperactivity disorder (ADHD) : implications for ADHD subtyping theory

Abstract

It is important to understand the neurobiological, cognitive, and behavioral factors that underlie ADHD and the ADHD subtypes. It has often been hypothesized that the ADHD-Combined Type (ADHD-CT) and ADHD-Predominantly Inattentive Type (ADHD-PI) subtypes may be the result of different underlying factors and may be associated with different types of attentional deficits. The current study compared 30 children with ADHD-CT and 35 children with ADHD-PI on several neuropsychological variables associated with various aspects of attentional processing. However, it is important to note that only 47 (22 with ADHD-CT and 25 with ADHD-PI) of the participants were assessed with some of the experimental measures. All participants were between the ages of 6 years, 0 months and 12 years, 11 months. Participants were evaluated using several neuropsychological measures associated with various aspects of attentional processing in order to test five hypotheses regarding possible subtype differences in specific types of attention. The attentional processes of interest included response activation, sustained attention, encoding/working memory, the focus/execute aspect of attention, and attentional stability. These constructs were taken from the theories of Tucker and Williamson (1984) and Mirsky and Colleagues (1999). The attentional measures used in this study were taken from the Test of Variables of Attention (TOVA), the Children’s Memory Scale (CMS), and the Wechsler Intelligence Test for Children-Third Edition (WISC-III). Analysis of possible subtype differences in the occurrence rate of reading disabilities was also conducted. Finally, post hoc analyses were conducted in order to test the hypothesis that specific attentional processes might impact other specific aspects of the neuropsychological functioning of children with ADHD. The attentional processes of interest were response activation and attentional stability. The dependent variables for the post hoc analyses included measures of language ability as well as behavioral ratings of attention and hyperactivity. No statistically significant group differences were found for any of the variables reflecting the five aspects of attentional processing. Nor were any significant subtype differences in the occurrence rate of reading disabilities or the post hoc analyses. The post hoc analyses did not yield statistically significant results either. Finally, weaknesses of the current study as well as future directions for ADHD research were discussed.