Sound Training Rewires Dyslexic Children's Brains For Reading

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Children With Dyslexic

Some children with dyslexia struggle to read because their brains aren't properly wired to process fast-changing sounds, according to a brain-imaging study published this month in the journal Restorative Neurology and Neuroscience.

The study found that sound training via computer exercises can literally rewire children's brains, correcting the sound processing problem and improving reading. According to the study's first author, Nadine Gaab, PhD, of the Developmental Medicine Center Laboratory of Cognitive Neuroscience at Children's Hospital Boston, the finding may someday help clinicians diagnose dyslexia even before reading begins, and suggests new ways of treating dyslexia, such as musical training.

Children with developmental dyslexia confuse letters and syllables when they read. The idea that they may have an underlying problem processing sound was introduced by Paula Tallal, PhD, of Rutgers University in the 1970s, but it has never been tested using brain imaging. Gaab used functional MRI imaging (fMRI) to examine how the brains of 9- to 12-year-old children with developmental dyslexia, and normal readers, responded to sounds, both before and after using educational software called Fast ForWord Language, designed in part by Tallal, a co-author on the study.

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Gaab first tested how the children's brains responded to two types of sounds: fast-changing and slow-changing. These sounds were not language, but resembled vocal patterns found in speech. As Gaab watched using brain fMRI, the children listened to the sounds through headphones. The fast-changing sounds changed in pitch or other acoustic qualities quickly--over tens of milliseconds--as in normal speech. By contrast, slow-changing sounds changed over only hundreds of milliseconds.

Infants must correctly process fast-changing sounds, like those within the syllable "ba," in order to learn language and, later, to know what printed letters sound like (see sound map). Infants use sound processing to grab from speech all the sounds of their native language, then stamp them into their brains, creating a sound map. If they can't analyze fast-changing sounds, their sound map may become confused.

"Children with developmental dyslexia may be living in a world with in-between sounds," says Gaab. "It could be that whenever I tell a dyslexic child 'ga,' they hear a mix of 'ga,' 'ka,' 'ba,' and 'wa'."

Reading trouble may develop when these children first see printed letters, Gaab and cognitive scientists believe, because at this stage, the children's brains wire their internal sound map to letters they see on the page. Linking normal letters to confused sounds may lead to syllable-confused reading.

But the brains of the children with dyslexia changed after completing exercises in a computer program known as Fast ForWord Language (Scientific Learning, Oakland, CA). The exercises involved no reading--only listening to sounds, starting with simple, changing noises, like chirps that swooped up in pitch. The children then had to respond--clicking to indicate, for instance, whether the chirp's pitch went up or down (See an example). The sounds played slowly at first--an easy task for the dyslexic children--but gradually sped up, becoming more challenging (See an example). The exercises then repeated with increasingly complex sounds: syllables, words, and finally, sentences.

The repetitive exercises appeared to rewire the dyslexic children's brains: after eight weeks of daily sessions--about 60 hours total--their brains responded more like typical readers' when processing fast-changing sounds, and their reading improved (See Image C). It's unclear, though, whether the improvement lasts beyond a few weeks, since follow-up tests were not done.

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