May 13, 1999. Copyright 1999. Graphic News. All rights reserved.

Dyslexia linked to brain abnormality
by Duncan Mil

LONDON, May 13 Graphic News: FOR MORE than 100 years scientists have been intrigued and frustrated by the paradox that some very bright people have profound and persistent difficulties in learning to read, write and spell. Dyslexia is one of the most common learning disorders and affects nearly one in 20 people. 

Now, new research published in The Lancet shows that abnormalities in an area of the brain called the cerebellum may play a key role in causing the disorder.

For the past decade the bulk of research into dyslexia has focused on the language centres of the brain, positioned in the cerebral cortex. However, there is now considerable evidence that, in addition to language, dyslexic children often have problems with rapid processing of information, together with coordination, balance and fluency.

Because it is one of the jobs of the cerebellum to help acquire new skills, and once learned, to make them automatic, it is thought likely that it also plays a part in articulation, skills for speech, eye movements needed for letter recognition and other automated processes related to reading, writing and spelling.

Professor Roderick Nicolson and co-workers at the University of Sheffield used a brain scan technique called positron emission tomography (PET) to monitor brain activity in six dyslexic adults and six adults without dyslexia Ð the control group.

Each subject lay with his/her head inside the PET machine while they performed a prelearned sequence of finger movements or learned a new sequence of finger movements, both with the right hand.

Professor NicolsonÕs team found that, compared with the brains of the control group, the brains of dyslexic adults showed much less activity in two specific areas. Activity in the cerebellum in dyslexic subjects was only around 10% of that of the controls. In addition, when performing the prelearned sequence, dyslexics showed less activity in the cerebellum and in the crescent-shaped cingulate gyrus Ð a supplementary motor area of the cerebral cortex.

The researchers say the findings suggest that a large number of dyslexic children have an abnormality of the cerebellum, adversely affecting learning new skills and automating skills associated with reading, writing and spelling. ÒOther parts of the brain may be involvedÓ, they say, Òbut the cerebellum is one key part of the brain affectedÓ.
/ENDS
Source: The Lancet