Chris, you seem convinced that balance and co-ordination problems are always part of dyslexia. I am not. Why? Among the people with dyslexia I know personally, few have balance/co-ordination issues. Many are superior athletes.
This is a good question and made me consider why I am so sure the cerebellum plays a significant part in causing dyslexia.
Firstly, personal experience. I was dyslexic with the usual range of symptoms: bad spelling and handwriting, poor short-term memory and poor coordination. My Mum was a primary school teacher and was one of the first people in the UK to get involved with Montessori method of teaching so I had plenty of help at home. Thanks to her efforts I learnt to read.
I struggled through secondary school and at times had special lessons and all the support a reasonably good state school can offer but by aged sixteen I was still a long way behind my peers. I failed my exams and dropped out of school. Having reached my mid-thirties with no real improvement in my dyslexic symptoms I embarked on the Dore method (it was called DDAT at that time). After fourteen months of exercises my spelling, handwriting, memory and coordination had all improved radically. It changed my life.
Personal experience is not scientific evidence. Placebo effects and a whole host of other tricks our mind can play on us make first person reports very poor evidence. However I can point to my last test for dyslexia and demonstrate my current abilities to show there is a clear, significant difference.
Secondly there is a lot of scientific. peer reviewed evidence that shows dyslexics (and people with other learning difficulties) have poor motor skills generally. Some studies have demonstrated that 80% of dyslexics have a cerebellar deficit. There is also evidence showing the cerebellum is involved in reading .
The combination of personal experience and a wide range of scientific evidence make me sure that the cerebellum plays a significant part in the cause of dyslexia in most sufferers. However dyslexia is not a single problem. There are also auditory and visual problems linked to dyslexia. In some people the cerebellum is the major problem with only very minor auditory and visual problems. Other people might have major auditory problems and only minor cerebellar issues. With dyslexics it is finding the right treatment for the individual (see The Log Jam Hypothesis) but I believe the starting point should be an exercise based programme.
Liz comments that she knows plenty of dyslexics that are superior athletes and thus would be expected to have good balance and coordination. This is true, many dyslexics make good sportsmen with great balance but the balance system isn’t simple. It involves the eyes, the vestibular system, the cerebellum, and the body. If the vestibular system is poor, other parts of the system can compensate, e.g. the eyes and cerebellum do most of the work and the person appears to have good balance. But if you disable the coping strategy by blind folding them or asking questions so that the cerebellum has to devote effort to other tasks, then the poor vestibular system become apparent.
A poor vestibular system makes the cerebellum work harder to compensate. This leaves limited amounts of mental resources for other tasks such as learning. A 747 has four engines but can fly perfectly well on one engine but it is an easier journey if all four engines are working.