Comorbidity of deficits in reading, spelling and arithmetic

Undiscovered comorbidities among children with specific developmental disorders are problematic, not only for clinical practice, but they provide a serious methodological problem for research: to identify neuro-cognitive deficits that might underlie a particular developmental disorder, groups of children who are diagnosed with that disorder are compared with normally developing control groups. However, a group difference might be due to a certain number of learning disabled children who have an additional, unidentified problem, e.g. a mild attention problem, while children who have the specific disorder only and no additional problems might perform on the same level as the control group. It is well known that developmental disorders co-occur frequently, however, such reports are usually based on clinical populations. The prevalence of comorbidities in the general school population needs as yet to be determined. This is the first aim of the proposed research project. The focus will be on deficits in reading, spelling, and arithmetic as well as comorbid attention deficits. Our second aim is to determine the neuro- cognitive and neuro-biological basis of developmental disorders and of their comorbidities. The specificity of current theories of causation of dyslexia (phonological deficit, automatization deficit, magnocellular deficit) and dyscalculia (deficit in basic numerical processing, deficit in executive functions and memory deficits) will be tested on large samples of children with both single and comorbid deficits in reading, spelling, arithmetic and attention. We predict that dyslexic children will show a specific deficit in the phonological domain and dyscalculic children will show deficits in the domain of basic processing of numerosities. Any other cognitive deficits will only occur in children with comorbid problems. Thus, we assume that learning disorders are largely independent from each other on the neuro-cognitive level. The frequent co-occurrence of these disorders could be due to a related genetic etiology which will be examined in an international cooperation with the genetics research group at the University Marburg and University of Bonn.

Undiscovered comorbidities among children with specific developmental disorders are problematic, not only for clinical practice, but they provide a serious methodological problem for research: to identify neuro-cognitive deficits that might underlie a particular developmental disorder, groups of children who are diagnosed with that disorder are compared with normally developing control groups. However, a group difference might be due to a certain number of learning disabled children who have an additional, unidentified problem, e.g. a mild attention problem, while children who have the specific disorder only and no additional problems might perform on the same level as the control group. It is well known that developmental disorders co-occur frequently, however, such reports are usually based on clinical populations. The prevalence of comorbidities in the general school population needs as yet to be determined. This is the first aim of the proposed research project. The focus will be on deficits in reading, spelling, and arithmetic as well as comorbid attention deficits. Our second aim is to determine the neuro- cognitive and neuro-biological basis of developmental disorders and of their comorbidities. The specificity of current theories of causation of dyslexia (phonological deficit, automatization deficit, magnocellular deficit) and dyscalculia (deficit in basic numerical processing, deficit in executive functions and memory deficits) will be tested on large samples of children with both single and comorbid deficits in reading, spelling, arithmetic and attention. We predict that dyslexic children will show a specific deficit in the phonological domain and dyscalculic children will show deficits in the domain of basic processing of numerosities. Any other cognitive deficits will only occur in children with comorbid problems. Thus, we assume that learning disorders are largely independent from each other on the neuro-cognitive level. The frequent co-occurrence of these disorders could be due to a related genetic etiology which will be examined in an international cooperation with the genetics research group at the University Marburg and University of Bonn.