Influence of comorbidity on working memory profile in dyslexia and developmental coordination disorder

ABSTRACT

Objective

Many studies report a deficit in working memory in children with Developmental Dyslexia (DD) and Developmental Coordination Disorder (DCD) compared to children with Typical Development (TD). In this study, we questioned the working memory profile of children with co-occurring Developmental Dyslexia and Developmental Coordination Disorder (DD-DCD). First, we hypothesized that children with DD would have a more substantial deficit in verbal working memory, while children with DCD would have a more substantial deficit in visuospatial working memory. For the comorbid group, we postulated a deficit in both the verbal and visuospatial domains. Second, we determined whether we could correctly distinguish between the four groups based on their working memory profiles.

Method

47 children with DD, 22 children with DCD, 27 children with DD-DCD, and 42 TD children aged from 7.6 to 12.6 years were tested on the phonological loop, the visuospatial sketchpad, and the central executive using the Digit Span and Wechsler’s Block-tapping tests.

Results

Children with DD had a deficit in verbal working memory including a specific deficit in the phonological loop and children with DCD had a deficit in visuospatial working memory. Comorbid children had poorer performance in verbal working memory (like group with DD) and in visuospatial working memory (like group with DCD). Exploratory cluster analysis resulted in four subgroups: (1) one cluster with good working memory performance made up of most of the TD children; (2) one cluster with a phonological loop deficit mainly made up of the children with DD; (3) one cluster with poor visuospatial working memory capacities mostly made up of the children with DCD (± DD) and (4) one cluster with average performance made up of children from all the groups.

Conclusion

Our results underline the importance of taking comorbidity into account when testing working memory in children with learning disabilities.

KEYWORDS:

• Neurodevelopmental disorder
• developmental dyslexia
• developmental coordination disorder
• comorbidity
• working memory

Acknowledgments

The authors are thankful to all the children and their parents who gave willingly of their time and effort. We also wish to thank Marie-Odile Livet, Virginie Michel, Mathilde Verriez for their involvement in the recruitment of some children, Melody Blais for her participation in the motor evaluation and Deborah Méligne for her help in the promotion of this study.

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes

1. Children with DCD have difficulties acquiring or executing motor coordination affecting gross and/or fine motor skills during their development, in the absence of neurological, neuromuscular or intellectual dysfunction (DSM-5, American Psychology Association, 2013).

2. Children with DD have a disorder affecting reading acquisition, characterized by a deficit in precision and/or fluency in written word recognition, which is not explained by a neurological, sensory or intellectual dysfunction (ICD-10, Worl Health Organisation, 1992 and DSM-5 American Psychology Association, 2013).

Additional information

Funding

This work was promoted by a grant from The French National Research Agency (ANR DYSTAC-MAP, ANR-13-APPR-0010-01); Agence Nationale de la Recherche [ANR-13-APPR-0010-01].