Frontal Systems Dysfunction in Children With Attention-Deficit/Hyperactivity Disorder and Learning Disabilities

Abstract

Tests of attention, inhibition, working memory, motor learning, and problem solving--functions associated with the brain's frontal systems--were administered to 26 children with attention-deficit/hyperactivity disorder and learning disabilities (ADHD + LD), 22 children with LD only, and 10 with ADHD only. Percentages of abnormal test results and significantly impaired scores were higher for the two groups with LD than for the ADHD-only group. The groups differed significantly on some tests of attention-inhibition-cueing, working memory, and problem solving, with the ADHD + LD and LD groups performing worse than the ADHD-only group. Abnormalities of frontal systems tests are not exclusive ADHD characteristics and are also present in LD children, implying a strong connection between centers of "processing" and centers of "executive" functions.

Working memory, response inhibition, and within-subject variability in children with attention-deficit/hyperactivity disorder or reading disorder

“…Consequently, working memory problems could have been mistakenly attributed to ADHD due to a high number of children with comorbid RD. It has been reported by others that when learning disabilities (LD) are controlled for, EF deficits are more prevalent in children with LD or comorbid LD+ADHD than in children with only ADHD (see Lazar & Frank, 1998). However, it must be noted that in the latter study the LD sample was not specific to reading problems alone.…”

“…It is therefore possible that EF deficits found in ADHD are due to comorbidity with another disorder (Pennington & Ozonoff, 1996). This makes it very important to control for comorbid disorders when trying to find out which deficits are a unique feature of ADHD (Banaschewski et al, 2005;Lazar & Frank, 1998;Sergeant et al, 2002).…”

The influence of working memory load on response inhibition in children with attention-deficit/hyperactivity disorder or reading disorder

“…Research on ADHD that has not taken into account the effect of RD, may have mistakenly attributed the deficit to ADHD (Lazar & Frank, 1998;Nigg, Hinshaw, Carte, & Treuting, 1998;Wu et al, 2002). Therefore, it will be important to control for this comorbidity when trying to find out which deficits are a unique feature of ADHD (Banaschewski et al, 2005;Lazar & Frank, 1998;Sergeant et al, 2002).…”

“…Therefore, it will be important to control for this comorbidity when trying to find out which deficits are a unique feature of ADHD (Banaschewski et al, 2005;Lazar & Frank, 1998;Sergeant et al, 2002). It will also be important to try to identify EFs that can distinguish between these disorders (Beveridge, Jarrold, & Pettit, 2002).…”

Differential motor alterations in children with three types of attention deficit hyperactivity disorder

“…The frontal systems are part of a broad network with connections to nearly all parts of the central nervous system (CNS). Therefore, possibly all cognitive systems are sensitive to frontal lobe pathology, i.e., ADHD 25 . The involvement of executive control includes, for instance, the ability to command motor exploration, to monitor and shift the direction of attention, to initiate and direct language, to organize methods of memorization, to temporally discriminate items in memory, and to inhibit interference during recall 26 .…”