Further Motor Deficits In Dyslexia

It is not only bimanual co-ordination tasks on which dyslexics may be impaired. The handwriting of dyslexic children is notoriously poor and on unimanual tasks, such as peg-moving or finger-tapping, disabled readers have sometimes been reported to perform worse than control participants of the same age (e.g., Badian & Wolff, 1977; Fawcett & Nicholson, 1995; Gardner & Broman, 1979; Wolff, Cohen, & Drake, 1984). It is not only dyslexic children who show sensori-motor impairments. Motor deficits reported by Fawcett and Nicolson (1995) were seen in dyslexics up to 17 years of age and adult dyslexics are slower in pointing with one hand to an unpredictable visual target (Velay, Daffaure, Giraud, & Habib, 2002). Findings such as these imply a persisting difficulty with certain fine motor skills.

Gross motor functions can also be affected. According to Miles (1993), dyslexics often have a history of difficulties in everyday tasks such as learning to ride a bicycle. Orton (1925) observed that "some of them give a history of delay in learning to talk and walk and of a lack of nicety of balance and consequent frequent falls and of indecision in the choice of the right or left hand in using the knife, fork and spoon, all of which speak for a definite delay in decisive dominant control of the motor mechanisms" (p. 595). He also noted that some of the children referred to him showed "evidence of mild apraxia" although, as Denckla (1985) remarked, there is a common tendency among some clinicians to use the word dyspraxia (or apraxia) rather liberally.

Orton's reference to a "lack of nicety of balance" is interesting in the light of research by Fawcett and Nicolson (1992) showing that dyslexic children find it more difficult than controls to balance on a beam with one foot while performing a secondary task (such as mental arithmetic). No difference between groups was observed when balancing was carried out without a concurrent task (see also Nicolson & Fawcett, 1990, 1994). However, the former result has proved difficult to replicate (Yap & van der Leij, 1994) and it may be that the deficit is more likely to show up in children who have attentional problems as well as reading difficulties (Wimmer, Mayringer, & Raberger, 1999).

Reporting the results of a series of experiments (Fawcett & Nicolson, 1992, 1995; Nicolson & Fawcett, 1990, 1994) carried out with children and adolescents drawn from local dyslexia associations, Fawcett and Nicolson (1995) claimed that dyslexic children (predominantly male) were significantly worse than reading age controls at threading beads and on a range of reaction time, balancing, and other motor tasks. Fawcett and Nicolson (1995) pointed out that the hypothesis that dyslexia involves primarily a phonological deficit cannot handle these findings. They therefore proposed that dyslexics are impaired in mastering skills which eventually come to be carried out automatically rather than under conscious control. Subsequently this "automatisation deficit" hypothesis became incorporated in their "cerebellar deficit" hypothesis (Nicolson, Fawcett, & Dean, 1995) although they were not the first authors to suggest involvement of the cerebellum in dyslexia (see Frank & Levinson, 1973; Levinson, 1988). Indeed, it has been argued in recent years that the cerebellum is involved not only in motor functions, as traditionally conceived (e.g., Holmes, 1917, 1939; Ito, 1993), but also in certain cognitive functions (Allen, Buxton, Wong, & Courchesne, 1997; De Schutter & Maex, 1996; Fabbro, Moretti, & Bava, 2000; Leiner, Leiner, & Dow, 1989, 1993; Schmahmann & Sherman, 1998) including reading (Brunswick et al., 1999; Fulbright et al., 1999), although this is a contentious issue (Glickstein, 1993; Ivry, 1996; Thach, 1997).

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Adult Dyslexia

Adult Dyslexia

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