Research PaperWorking memory functioning in children with attentiondeficit/hyperactivity disorder (ADHD): A comparison between subtypes and normal controls

Abstract

Objective: Children with attention-deficit/hyperactivity disorder (ADHD) often experience working memory difficulties. However, research findings are inconsistent, making it difficult to compare results across studies. There are several reasons for this inconsistency. Firstly, most studies make no distinction between ADHD subtypes, despite evidence that predominantly inattentive ADHD (ADHD/I) represents a different neurocognitive profile to the hyperactive-impulsive subtype (ADHD/HI). Secondly, documented studies use different tests of working memory which may be measuring different skills. Some assess only the verbal components of working memory and others the visuo-spatial; few of the tests assess both. Further, some tests employ a recognition methodology and others use recall, which require different brain regions and cognitive processes. To clarify these inconsistencies, the verbal and visuo-spatial working memory of children with ADHD/I, ADHD/HI and a control group with no ADHD symptoms were compared.
Method: The Automated Working Memory Assessment and Ravens Coloured Progressive Matrices were administered to 72 children (ADHD/I n = 27; ADHD/HI n = 25; control n = 20).
Results: The ADHD groups performed similarly, but were significantly poorer than the control group in all aspects of working memory. Storage abilities were stronger than processing abilities, while verbal and visuo-spatial abilities were equally developed for all groups.
Conclusion: ADHD-related deficits were apparent across working memory components, even when IQ was controlled for, suggesting a generalised impairment.

Journal of Child and Adolescent Mental Health 2011, 23(2): 107–118