Cognitive subtypes of dyslexia

Stefan Heim^1,2*, Julia Tschierse³, Katrin Amunts^1,2,4, Marcus Wilms¹, Simone Vossel^1,2, Klaus Willmes⁵, Anna Grabowska⁶ and Walter Huber³

¹Research Centre Jülich, Institute of Neurosciences and Biophysics, Jülich, Germany; ²Brain Imaging Center West (BICW), Jülich, Germany, *Email: s.heim@fz-juelich.de; ³Department of Neurolinguistics, RWTH Aachen, Germany; ⁴Department of Psychiatry and Psychotherapy, RWTH Aachen, Germany; ⁵Department of Neuropsychology, RWTH Aachen, Germany; ⁶Nencki Institute of Experimental Biology, Warsaw, Poland

Abstract. Different theories conceptualise dyslexia as either a phonological, attentional, auditory, magnocellular, or automatisation deficit. Such heterogeneity suggests the existence of yet unrecognised subtypes of dyslexics suffering from distinguishable deficits. The purpose of the study was to identify cognitive subtypes of dyslexia. Out of 642 children screened for reading ability 49 dyslexics and 48 controls were tested for phonological awareness, auditory discrimination, motion detection, visual attention, and rhythm imitation. A combined cluster and discriminant analysis approach revealed three clusters of dyslexics with different cognitive deficits. Compared to reading-unimpaired children cluster no. 1 had worse phonological awareness; cluster no. 2 had higher attentional costs; cluster no. 3 performed worse in the phonological, auditory, and magnocellular tasks. These results indicate that dyslexia may result from distinct cognitive impairments. As a consequence, prevention and remediation programmes should be specifically targeted for the individual child's deficit pattern.

Keywords: cluster, reading, attention, phonology, automatization, magnocellular, auditory, diagnostics