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Disruption found in brain circuitry of dyslexics WASHINGTON (March 2, 1998 9:12 p.m. EST http://www.nando.net) -- Medical imaging techniques that look into the brain's inner workings show for the first time that a part critical to reading has an impaired function in people with dyslexia. "This provides evidence that dyslexia is a real biological entity," said Dr. Sally E. Shaywitz, a Yale University School of Medicine researcher. She described the problem as "a glitch in the circuitry for reading" that makes it more difficult for dyslexics to link printed letters and words instinctively with the language sounds the letters and words represent. Such linkage, said Shaywitz, is essential for learning to read and is accomplished routinely in people with a normal connection between parts of the brain that control language and vision. Shaywitz is lead author in a study to be published Tuesday in the Proceedings of the National Academy of Sciences. To identify the brain circuitry problem, Shaywitz and her colleagues used a technique called functional magnetic resonance imaging. This technology allows researchers to observe which parts of a subject's brain are active when a specific function is performed. The researchers used the MRI technique on 29 dyslexic readers and 32 normal readers. They were all required to read a list of nonsense words that would rhyme if the reader could correctly link the letters with the language sounds that they symbolize. Shaywitz said there are 44 letter sounds in the English language. They are represented by 26 letters in the alphabet, either singly or in combination. In order to read, a person's brain must convert the printed letters into the sounds they represent. In the functional MRI tests, Shaywitz said normal readers showed activity in both the portion of the forebrain that processes visual information, and in the back of the brain that contains the language center. And normal readers had no trouble interpreting the rhyming symbols and sounds. For dyslexics, however, there was reduced activity in the language center at the back of the brain and increased activity in a part of the brain linked to the spoken word. And they much less able to link the rhyming letters and sounds. Shaywitz said the MRI study provides physical evidence for one of the major problems dyslexics have in learning to read: individually identifying the 44 letter sounds in the English language and linking those sounds to their alphabetical symbols. As an illustration, she said dyslexics may hear language as a blur of sounds, rather like the way a nearsighted person looks at a red brick wall and sees only a blur of color. A normal person, said Shaywitz, is able to discern the individual language sounds in the same way that a person with good vision could see the individual red bricks in the wall. Copyright 1998 Nando.net Copyright 1998 The Associated Press janet paterson 50-9 / sinemet-selegiline-prozac almonte-ontario-canada / [log in to unmask]