ERP correlates of selective attention and working memory capacities in children with ADHD and/or PDD-NOS.

OBJECTIVE We examined whether children (8-11 years) diagnosed with Pervasive Developmental Disorder-Not Otherwise Specified (PDD-NOS) or Attention-Deficit/Hyperactivity Disorder (ADHD) showing primarily hyperactive behavior, differed in selective attention and working memory (WM) abilities. METHODS Healthy controls and children with ADHD, PDD-NOS or symptoms of both disorders (PDD/HD) (n=15 in each group) carried out a visual selective memory search task while their EEG was recorded from which event-related potentials were derived. RESULTS Compared to the control group, all patient groups made more omissions while hyperactive children also exhibited more false alarms. Regarding the process of WM-controlled search, significant group differences in ERP data were found between the control group and each of the clinical groups. CONCLUSIONS The results point to less efficient WM-functioning in all patient groups. Whereas the clinical groups differed from each other at the behavioral level as measured by questionnaires, no distinction between the clinical groups could be made with respect to performance or ERP measures of WM capacity and selective attention. SIGNIFICANCE The results suggest that a possible differentiation in selectivity and working memory capacities between PDD-NOS and ADHD is hard to find. This may agree with clinical practice, where differential diagnosis is a subject of discussion.