Dyslexia Linked to Brain Malfunction

For the first time, scientists have been able to identify specific brain malfunctions involved in dyslexia--a discovery that could substantially improve understanding of the chronic reading problem that afflicts about 10 million Americans.

Equally important, said lead researcher Sally E. Shaywitz of Yale University School of Medicine, the work provides scientific confirmation “for what has previously been a hidden disability.”

“If you break your arm, you can hold up an X-ray and see it,” she said. “But I get calls from distraught parents and even teachers who say, ‘My school system denies that there’s such a thing as dyslexia.’ Well, now they can say, ‘Here’s the evidence.’ ”

Using high-tech imaging equipment, Shaywitz’s team found that the brains of dyslexic subjects show very little activity in areas known to be highly important in linking the written form of words with their phonic components.

In their work reported in today’s issue of Proceedings of the National Academy of Sciences, Shaywitz and colleagues used a brain-mapping procedure called functional magnetic resonance imaging (fMRI) to monitor mental activity in 61 subjects. Like the MRI scans familiar to many patients, fMRI provides an image of internal body structures in very fine resolution. But it also shows which parts of the brain are most active at a given time.

The subjects were given five kinds of exercises. Each required progressively greater effort in processing the sound aspects of written language, as distinct from merely recognizing shapes, letters or words. One task, for example, asked whether several nonsense words (such as “leat” and “jete”) would rhyme--a difficult problem for dyslexics.