Researchers present on working memory training at AACAP meeting

Research title: Research Symposium on Working Memory and ADHD held at 2008 Meeting of the American Academy of Child and Adolescent Psychiatry

Researchers: Rosemary Tannock, Torkel Klingberg, Jeff Halperin, Anne-Claude Bedard

Training program used in research: Cogmed RM

Published: AACAP, November 2008

Overview
The 2008 meeting of the American Academy of Child and Adolescent Psychiatry included a research symposium titled “An Overview of Working Memory in ADHD”. A summary of the papers presented at this symposium is provided below.

Paper 1

“Functional Significance of Working Memory and Its Link with Inattention and ADHD”
The first paper in this symposium is titled “Functional Significance of Working Memory and Its Link with Inattention and ADHD” and was presented by Dr. Rosemary Tannock of the University of Toronto.

Dr. Tannock notes that “Working memory is defined as the capacity to briefly hold and manipulate information no longer accessible in the environment. This capacity to hold and use information in mind for a few seconds is required for most complex activities, such as problem-solving, following a conversation, or keeping track of remembering a sequence of instructions. Poor WM predicts poor literacy and numeracy outcomes in school-aged children.”

In her paper, Dr. Tannock presented results from a meta-analysis of 26 studies of WM involving children and adolescents with ADHD and age-matched typically developing children. Results of her analysis indicated marked reductions in WM performance relative to controls WM in both visual-spatial and auditory-verbal domains.

Dr. Tannock reported on her own studies of WM in college students with ADHD where she found that despite their academic success evident by attention college, both males and females with ADHD had multiple deficits in WM. Her work with college students also indicated that WM is more strongly associated with inattention than hyperactivity and that WM predicts academic outcome, as indicated by Grade Point Average. Finally, she described a study of 140 7-12 year-old children in which results indicated that poorer performance on WM tasks predicted high parental ratings of inattentive behavior (but not hyperactive/impulsive or emotional problems) in both males and females.

Dr. Tannock concluded that WM is impaired in ADHD and should be a domain of inquiry in the clinical assessment of ADHD. Based on her data, she estimates that 30-40% of individuals with ADHD have a clinically significant impairment in WM.

Paper 2

“Working Memory in a Longitudinal Sample of Adolescents/Adults Diagnosed with ADHD in Childhood”
In the second paper titled “Working Memory in a Longitudinal Sample of Adolescents/Adults Diagnosed with ADHD in Childhood” Dr. Jeff Halperin of Queens College examined the stability of working memory in a longitudinal sample of youth with ADHD; he also tested whether childhood working memory deficits predict later clinical severity.

At the start of this study, WM was assessed in 98 7-11 year old children with ADHD using the Digit Span test (children are read a string of digits and have to repeat them correctly in forwards or backwards order). Approximately 9 years later, WM performance and ADHD symptoms were reassessed.

Results indicated that WM performance showed good stability over the 9-year period, especially Digit Span backwards. In addition, children’s performance at baseline on Digit Span backwards predicted the severity of parents’ ratings of attention problems at the 9-year follow-up (r = -0.32, p = 0.005).

Dr. Halperin concluded that WM is a reasonably stable trait that may play an important role in the persistence of ADHD. He suggested that treating working memory deficits early on may have the potential to change the trajectory for children with the disorder.

Paper 3
“Impact of Methylphenidate on Working Memory in ADHD”
In the third paper titled “Impact of Methylphenidate on Working Memory in ADHD” Dr. Anne-Claude V. Bedard from the Mt. Sinai School of Medicine discussed the effects of methylphenidate (MPH) on components of working memory (WM) in ADHD. Her work also examined the influence of comorbidity on these effects and assessed the responsiveness of WM measures to MPH effects. S

Dr. Bedard reported results from three double-blind, randomized, crossover studies to examine the impact of immediate-release MPH on established WM tasks in children with ADHD. Her findings indicate that MPH has selective effects on WM – that not all aspects of WM are improved, and not all WM measures are responsive to its effects. She also reported that in children with comorbid anxiety, benefits of methylphenidate on WM performance were not found.

Paper 4

“Computerized Training of Working Memory in Children with ADHD”
The final paper by Dr. Torkel Klingberg titled “Computerized Training of Working Memory in Children with ADHD” presents data from 2 studies that test whether WM can be improved with intensive computerized training, i.e., Working Memory Training. (Disclosure – Dr. Klingberg is the developer of Cogmed Working Memory Training; Attention Research Update receives financial support from Cogmed.)

In study 1, 53 children with ADHD were randomly assigned to an active WM training condition or a control condition where training was less intensive. In the treatment program, children practiced WM tasks in which the difficulty level was adjusted to closely match the WM capacity of the child. Training was done via computer 5 days/week for 5 weeks with each session lasting 30-40 minutes. Exercises are designed to train both the visual-spatial and auditory-verbal WM. The difficulty level is automatically adjusted, on a trial by-trial basis, to match the WM span of the child on each task.

In the control condition, the same tasks were used, but the difficulty did not increase or adjust to the child’s performance. WM capacity of the child is not challenged and there is no reason to expect a training benefit.

The effect of training was measured using tasks that were not part of the training program, which included (1) The span-board task from the WAIS-RNI testing battery to measure visual-spatial WM, and (2) the digit-span task from the WISC-III testing battery to measure auditory-verbal WM.

Results indicated that the treatment group improved significantly more than the comparison group on the non-trained working memory tasks. This was evident immediately following training as well as 3 months later. Treatment effects were also found for response inhibition using the Stroop task, auditory-verbal WM (digit-span), and complex reasoning (Raven’s task). Finally, WM training also had a strong effect on parent ratings of children’s attention; however, a similar effect was not found for teacher ratings.

Participants in the second study were children with ADHD (any subtype) using medication (N = 66, 6 girls, age 11.6 (SD 2.1)) and without medication (N = 70, 7 girls, age 11.5 (SD 2.0)). Both groups completed 25 days of computerized training on working memory tasks; children in both groups received the intensive WM training, i.e., this was not a randomized-controlled trial and there was no comparison group that received “sham” training.

Results indicated that medicated and non-medicated children improved on the trained tasks and showed a decrease in ADHD-symptoms. Compared to non-medicated children, children on medication showed a significantly greater improvement on visual-spatial WM tasks. This difference was not observed for verbal WM tasks. There was also a trend for larger reduction of ADHD symptoms in the medicated group. These findings suggest that cognitive training may enhance the benefits of medication treatment in children with ADHD.

Summary and Conclusions
These papers add to our growing knowledge of the role of WM deficits in ADHD. As discussed by Dr. Tannock, significant WM deficits are found in 30-40% of individuals with ADHD; Dr. Halperin’s work provides initial evidence that WM is relatively stable over time in children with ADHD and that poor WM performance predicts continuity of attention difficulties over 9 years. The final 2 papers report on medical and cognitive training interventions; it appears that medication treatment improves selective aspects of WM, that WM is an ability that can be improved with intensive training, and that the combination of medication and WM training may yield greater benefits for some children with ADHD. This is an interesting area of work that is garnering increasing interest from both researchers and clinicians.