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As researchers look more
carefully at the 5 to 15 percent of children in the United States who have dyslexia, they're
finding there's no single disease
"dyslexia," but rather many dyslexias resulting from unique combinations of genes, mechanisms and changes in the brain. They're also finding that each has an optimal treatment.
Through brain imaging and genetic studies, Children's Hospital Boston researchers are pinning down the
mechanisms involved in different types of dyslexia. Nadine Gaab, PhD, of the Developmental Medicine Center
Laboratory of Cognitive Neuroscience, with Elise Temple of Dartmouth College, found that children with developmental dyslexia, whose reading problems stem from a faulty understanding of the sounds that make up their native language, may lack the proper brain wiring to process fast-changing sounds. While this idea was first proposed in the 1970s, it hadn't been proven using brain imaging in children. According to the theory, infants whose brains can't analyze fast changes within sounds don't properly learn the sounds of language. They miss, for instance, the 40-millisecond pitch sweeps that differentiate "ba" and "da." This leads to a confused sound map in the brain. Later, when these children first try reading, they link the
letters to this confused sound map. // cont.
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