In “Dyslexia, Dysgraphia, Procedural Learning and the Cerebellum,” Roderick Nicolson and Angela Fawcett present a fascinating and, to me, strong argument for unifying theoretical views of dyslexia and dysgraphia. To be sure, their analysis is preliminary and basic, but my first read left me feeling as if they’d hit lots of good points. They’ve emphasized impairment of automatic procedural learning in the cerebellum at the level of neural circuits, but in dysgraphia the problems are with motor circuits and in dyslexia they are in the language circuits. In developing their case, they integrate a broad range of neurological and psychological research.
Sphere: Related ContentIn this review we focus on the developmental disorders of dyslexia (a disorder of reading) and dysgraphia (a disorder of writing), considering their commonalities and differences with a view to reflecting on the theoretical implications. Interest in dysgraphia was stimulated by the distinction between phonological and surface dyslexia (Castles and Coltheart, 1993), which claimed that orthographic problems (spelling) were separable from phonological reading problems. While this distinction has received mixed support ([Snowling et al., 1996] and [Stanovich et al., 1997]) it led to a fruitful analysis not only of the underlying causes of orthographic difficulties, but also to the widespread recognition of developmental difficulties in handwriting control ([Deuel, 1995], [Manis et al., 1996] and Sprenger-Charolles et al., 2000 L. Sprenger-Charolles, P. Cole, P. Lacert and W. Serniclaes, On subtypes of developmental dyslexia: Evidence from processing time and accuracy scores, Canadian Journal of Experimental Psychology-Revue Canadienne De Psychologie Experimentale 54 (2000), pp. 87–104. Abstract | Full Text via CrossRef[Sprenger-Charolles et al., 2000]). The result of this theoretical and empirical progress is that there are two usages of the term dysgraphia. One takes dysgraphia to refer to errors of writing that are analogous to errors in reading (e.g., surface, phonological or deep dysgraphia corresponding to surface, phonological and deep dyslexia), the other relating to difficulties in handwriting control. Furthermore, despite these attempts at differentiation, there remains some controversy in the literature as to whether motor difficulties in handwriting should be subsumed under the label dyslexia.
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Subtyping LD
Have you been hearing a lot about subtypes of LD lately? Perhaps it’s just that I’ve been especially alert to it, but it seems I’ve heard a lot of mentions about subtypes of Learning Disabilities in the last few weeks. I want to write a longer, more thorough discussion of the topic, but I’ve found myself repeating a few foundational comments, so I thought I ought to post them here and let others have a go at them.
First, the idea of subtypes of LD is essentially a given. It has to do with the heterogeneity of LD. Because LD is essentially an umbrella category for a diverse array of learning disabilities (note the plural), there are bound to be subgroups. Some students will have problems primarily with reading, some primarily with arithmetic and mathematics, some with writing, others with combinations of these. That makes for lots of subgroups right there. That is, one could start with dyslexia, dyscalculia, and dysgraphia!
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