Executive Functions in Neurodevelopmental Disorders: Comorbidity Overlaps Between Attention Deficit and Hyperactivity Disorder and Specific Learning Disorders

The present study examines the comorbidity between specific learning disorders (SLD) and attention deficit and hyperactivity disorder (ADHD) by comparing the neuropsychological profiles of children with and without this comorbidity. Ninety-seven schoolchildren from 8 to 14 years old were tested: a clinical sample of 49 children with ADHD (n = 18), SLD (n = 18) or SLD in comorbidity with ADHD (n = 13), and 48 typically-developing (TD) children matched for age and intelligence. Participants were administered tasks and questionnaires to confirm their initial diagnosis, and a battery of executive function (EF) tasks testing inhibition, shifting, and verbal and visuospatial updating. Using one-way ANOVAs, our results showed that all children in the clinical samples exhibited impairments on EF measures (inhibition and shifting tasks) when compared with TD children. A more specific pattern only emerged for the updating tasks. Only children with SLD had significant impairment in verbal updating, whereas children with ADHD, and those with SLD in comorbidity with ADHD, had the worst performance in visuospatial updating. The clinical and educational implications of these findings are discussed.

Offering alphabet support in the Trail Making Test: Increasing validity for participants with insufficient automatization of the alphabet

Insufficient automatization of the alphabet may falsely impair performance on the Trail Making Test among persons with dyslexia or persons not accustomed to the Latin alphabet. We analyze whether writing the alphabet on top of the test sheet changes performance in these risk groups, and whether alphabet support reduces the complexity of the set-shifting task.One-hundred and seventy patients referred to neuropsychological assessment participated and were given both a TMT-version offering alphabet support and the D-KEFS TMT. The discrepancy between the D-KEFS subtask where lines are drawn successively between numbers only, and the task where lines are drawn between letters only, was operationalized as measuring insufficient alphabet automatization.Both the possible dyslexia group, and persons taught to read with another alphabet, had a larger discrepancy score than the remaining sample. Regression analyses showed that the discrepancy scores explained 3.4% of the variance beyond age and speed when giving alphabet support. The corresponding percentage for the D-KEFS Switching task was 17.5%. The findings indicate that alphabet support alleviated effects of non-automatization. The TMT-B-NR: TMT-A ratio score was equivalent to what is found when not applying alphabet support, showing that alphabet support did not contaminate the test as a EF-measure.

Comorbidity of reading disabilities and ADHD: Structural and functional brain characteristics

Reading disabilities (RD) and attention-deficit/hyperactivity disorder (ADHD) are two of the most common developmental disorders. RD and ADHD frequently co-occur, which raises questions about how the disorders interact and to what extent they can be differentiated. To date, the underlying neural mechanisms leading to RD-ADHD comorbidity (COM) are not understood. In this study, structural and functional magnetic resonance imaging (fMRI) were combined with comprehensive behavioral testing in order to characterize the behavior, brain structure, and neural correlates of executive function, phonological processing and reading fluency in 60 children with clinical diagnoses of RD, ADHD, or COM, and controls. Whole-brain analyses of variance were performed on cortical thickness values and on the data of the three fMRI tasks to investigate overall group differences. To validate these findings, a region of interest analysis was performed in regions that have previously been shown to exhibit group differences in children with RD or ADHD using the same paradigms. The neuroimaging results demonstrated structural and functional atypicalities for COM in regions that are frequently associated with deficits in children with isolated ADHD or RD. A combination of shared and distinctive brain alterations between the clinical groups was identified, supporting the multiple deficit model for ADHD, RD, and its comorbidity.

Occupational Status Is Compromised in Adults With ADHD and Psychometrically Defined Executive Function Deficits

OBJECTIVE

Problems related to executive function (EF) are frequently reported in adults with ADHD. However, only a subgroup of patients show deficits on common neuropsychological tests designed to measure EF. We investigated whether this subgroup also had higher levels of functional impairments, including unemployment, than the ADHD group without such deficits.

METHOD

We defined executive function deficit (EFD) from selected tests from the Delis-Kaplan Executive Function System (D-KEFS) and assessed ADHD symptoms and psychiatric comorbidity with the use of questionnaires in 79 ADHD patients and 77 controls (IQ above 80 in both groups).

RESULTS

In the ADHD group, 24.3% had EFD. This subgroup showed significantly higher frequency of unemployment, more reading and writing problems, lower IQ scores, and more self-reported ADHD symptoms in childhood than the ADHD subgroup without EFD.

CONCLUSION

These findings indicate that it may be possible to identify individuals at risk of functional impairments, and emphasizes the importance of effective treatment programs targeting EF.

Cognitive Processes in ADHD and Asperger's Disorder: Overlaps and Differences in PASS Profiles

OBJECTIVE

Many studies report on the usefulness of the evaluation of Executive Functions (EF) in the assessment of participants with ADHD, while others underline how deficits of EF in these participants are not consistent and that the same executive deficits are present in many other disorders, particularly in Asperger's disorder. Using the Planning Attention Simultaneous Successive (PASS) theory, the present study explores the cognitive profiles of participants with ADHD or Asperger's disorder and compares the cognitive functioning of these two diagnostic groups.

METHOD

Forty-four children, 24 with a diagnosis of ADHD and 20 with a diagnosis of Asperger's disorder, participated and their cognitive processes were evaluated with the Cognitive Assessment System.

RESULTS

Results underline specific cognitive profiles in ADHD and Asperger's disorder characterized by weaknesses in planning and attention, but with a diverse level of severity.

CONCLUSION

Implications of the different cognitive profiles of these diagnostic groups are discussed.

Executive Function, Self-Regulated Learning, and Reading Comprehension: A Training Study

The goal of this study was to evaluate the extent to which training that emphasizes the process of executive function (EF) and self-regulated learning (SRL) would result in increased reading comprehension; we also evaluated interrelationships of EF, SRL, and reading. We report an experiment ( N = 75 fourth graders) that contrasted two researcher-implemented conditions (text-based reading [TB] and text-based reading plus executive function [TB+EF]) to a control. We also evaluated relationships among measures of SRL, EF, and reading. Both the TB and TB+EF groups outperformed the control group for proximal text comprehension (where the topic was similar to that covered in training) and background knowledge related to it, but the two researcher-led groups performed similarly. There were no significant differences for less proximal text, and again similar performance for both TB and TB+EF. Correlations among measures were weak in general, although the pattern was similar to that found in the extant literature. The findings speak to the difficulty in separating these components from those of strong instruction more generally. The relationships of these constructs to reading comprehension will likely be enhanced by more sensitive measurement of EF and reading comprehension, particularly where tied to active treatment components.