Similarly, following the cerebellar deficit hypothesis of dyslexia (Nicolson, Fawcett & Dean, 2001), Dore and Rutherford (2001) have proposed that given the plasticity of the cerebellum throughout childhood, it should be possible to retrain the dyslexic cerebellum, leading to more normal functioning, such that learning is scaffolded much more efficiently. They have since developed a systematic Balance Remediation Training Programme, DDAT, based on longstanding principles of balance.
Key elements of the exercise treatment include the use of a balance board, throwing and catching of bean bags (including throwing from hand to hand with careful tracking of the eye), and the practice of dual tasking. In a recent evaluation of this DDAT exercise-based treatment for children with reading difficulties, it was concluded that, in addition to its direct effects on balance, dexterity and eye movement control, the benefits of treatment extended to the cognitive skills underlying literacy and the reading process (Reynolds , Nicolson & Hambly, 2003).
In conclusion it can be concluded that, to a large extent researchers agree that a phonological deficit, and the phonics instruction that follows, is the cause and the most beneficial form of remediation, respectively. This is reflected in the predominance of the phonology in dyslexia research and practice for the past 20 years. However a rival area of dyslexia research has challenged this consensus. Although these researchers do agree on the existence of a phonological deficit in dyslexia, their primary focus on sensory and motor impairments in dyslexia has generated very different hypotheses to that of the phonological deficit hypothesis.
The lurking question is that of whether they are all correct and co-existable. It is presently argued that the differences between dyslexia researchers need to be resolved as a better understanding of the causes and remediation of dyslexia is likely to lead to the development of better diagnostic procedures, early detection, and successful conquering of the disorder. Resolution could be achieved, perhaps through further research into the possibility of subtypes of developmental dyslexia.
The hitherto research in this domain has distinguished between two subtypes, phonological dyslexia and surface dyslexia, where on the basis of the two-route model of reading development, there is damage to the phonological (spelling-to-sound) route, and the visual (whole word) route respectively (Manis, Seidenberg, Doi, McBride-Chang & Petersen, 1995). It could be then that different dyslexic research, especially concerning phonological, auditory and visual impairments, is studying different types of dyslexics. However more extensive research does need to be carried out regarding the issue of subtypes and the underlying causes of dyslexia.
The occurrence of sensory and/or motor disorders more often in the dyslexic than in the non-dyslexic population gives rise to the possibility that dyslexia could be viewed as a general sensorimotor syndrome, as opposed to a specific phonological deficit on the other side of an antagonistic divide. However the prevalence is limited in comparison to that of a deficit in phonological processing. Indeed a recent large scale study (Ramus, Rosen, Dakin, Day, Castellote, White, & Frith, 2003), has found every single dyslexic in their sample to display a phonological deficit, with a third of them seeming to be spared by any concurrent sensory or motor deficit.
Another caveat of the proposed sensory and motor disorders is that they seem to have limited consequences on reading skill. The relationship of visual deficits to reading retardation, for example, is hotly debated, especially as visual disorders are frequently accompanied by a phonological deficit. The visual, along with the rest of the sensory and motor hypotheses outlined above are very controversial and overall very different to the largely held phonological deficit.
It is therefore unlikely that they will all be able to peacefully co-exist. But until one side of the antagonistic divide decides to give in or are proved wrong it doesn’t seem like their will be any long-term resolution. In the meantime based on this current knowledge, Franck Ramus (2003) proposes a viable immediate resolution, that is the characterisation of dyslexia as a specific phonological deficit, optionally accompanied by a sensorimotor syndrome. Consequently whether or not the remediaition of the dyslexic individual will involve additional or alternative interventions to the successful phonics instruction, will depend on the absence or presence of this optional feature.
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