A test of the integrity of the components of Baddeley's model of working memory in attention-deficit/hyperactivity disorder (ADHD)

BACKGROUND: The integrity of working memory in attention-deficit/hyperactivity disorder (ADHD) was tested within the framework of Baddeley's model. METHODS-1: Buffers and rehearsal mechanisms were assessed by presenting children with or without ADHD (ages 8 to 15) with 1-7 target letters and a probe after 2-10 s. They decided if the probe was the same (verbal task) or in the same location (spatial task) as any of the targets. RESULTS-1: There was no interaction between group and delay or memory load in either task. METHODS-2: The central executive was assessed on a dual task. RESULTS-2: Although children with ADHD did not differ from controls in simple response time (RT) or in digits recalled, they showed greater decrements in RT when performing the 2 tasks concurrently. CONCLUSIONS: Findings suggest that children with ADHD (1) do not have generalized impairments in working memory, (2) rehearse verbal and spatial information in the same manner as healthy children, (3) may have an impairment in the central executive component of working memory, which controls ability to divide attention between two tasks.     

Response Inhibition in AD/HD, CD, Comorbid AD/HD+CD, Anxious, and Control Children: A Meta-analysis of Studies with the Stop Task

The aim of this study was to investigate whether impaired response inhibition is uniquely related to AD/HD or whether deficits in response inhibition are also evident in other psychopathological disorders. Furthermore, the suggestion was examined that anxiety disorders are associated with abnormally high levels of response inhibition. This paper presents the results of a meta-analysis of eight studies in which response inhibition was assessed with the so-called stop task in five groups of children: children with attention deficit/hyperactivity disorder (AD/HD), children with conduct disorder (CD), children with AD/HD+CD, children with anxiety disorders, and control children. A total of 456 children participated in the 8 studies. All children were in the age range 6–12 years. Consistent and robust evidence was found for a response inhibition deficit in AD/HD. However, response inhibition deficits did not distinguish children with AD/HD from children with CD, nor from children with comorbid AD/HD+CD. Contrary to predictions, anxious children did not demonstrate enhanced levels of response inhibition.