By Steve Connor, The Independent, London
LONDON -- A region of the brain known as the body's autopilot,
because it allows us to carry out complex movements without
thinking too hard, has been linked to dyslexia, the learning
disorder that affects one child in twenty.
Scientists have identified abnormal activity in the cerebellum
of dyslexics, which could account for why they must concentrate far
harder on reading than non-dyslexic people, a finding that may lead
to better pre-school tests for the condition.
The research could explain why dyslexic children tend to be more
clumsy and why they find it more difficult to carry out
``automatic'' movements that other people take for granted, such as
driving while talking, and playing sports such as tennis where
movement in relation to other people or objects is important.
Rod Nicholson, a psychologist at the University of Sheffield who
made the five-year study, told the British Association that several
lines of evidence point to a ``deficit'' in the activity of the
cerebellum as the probable cause of dyslexia.
``Of course automatization is a key requirement for reading, and
there is extensive evidence that dyslexic children, even when
reading well, are less fluent, requiring more time and effort to
read than would a non-dyslexic child of the same reading age.
``We have used the analogy of driving in a foreign country - one
can do it, but it requires continual effort and is stressful and
tiring over long periods. On our account, life for a dyslexic child
is like always living in a foreign country.''
The most startling finding, Professor Nicholson said, was that
dyslexic children are significantly worse at balancing, a highly
automatic ability not obviously connected to reading. ``We found
that although a group of dyslexic adolescents were normally able to
balance as well as non-dyslexic children their balance deteriorated
very significantly when they had to do something else at the same
time.''
Tests designed to reveal low cerebellum activity showed
significantly greater ``deficits'' in 80 per cent of dyslexic
children, a finding Professor Nicholson described as unexpected,
because previous studies have concentrated on the cerebral cortex,
which is known to be involved in learning.
A second study using a brain scanner revealed that dyslexic
adults had 10 per cent of the cerebellum activity of non-dyslexics
when performing tasks involving automatic control, namely learning
a sequence of finger movements.
Professor Nicholson said an analysis of brains stored at the
International Dyslexia Association Brain Bank in Boston,
Massachusetts, found dyslexics had larger than average nerve cells
in the cerebellum. ``We believe we now have a coherent account of
the major symptoms, the underlying cause and the way the reading
problems develop ... there appear to be remarkably few loose ends.
``If the underlying cause can be established, then it should be
possible to diagnose dyslexia pre-school, thereby giving the
opportunity to provide initial reading support better tuned to the
way that dyslexia children learn best,'' Professor Nicholson said.
