SUNDAY, Nov. 9, 2003 (HealthDayNews) -- Dyslexia may be more than a problem of unscrambling the written word. It may stem from a glitch in how the brain processes sight and sound together, a new study suggests.
The research provides evidence that dyslexia is a "multi-sensory" disorder, as opposed to either a problem interpreting visual cues or difficulties involving language areas of the brain.
The finding could lead to a simple test for diagnosing dyslexia in children "even before they have the capacity to read," says study leader Mark Wallace, an associate professor of neurobiology and anatomy at Wake Forest University Baptist Medical Center.
Wallace reported his preliminary findings Nov. 9 in New Orleans at the annual meeting of the Society for Neuroscience, the world's largest organization of brain scientists.
Because dyslexia often goes undiagnosed, estimates of the number of children and adults in the United States who struggle with the learning disability vary greatly. Wallace says 5 percent to 10 percent of the general population is affected. Others believe the proportion could be as high as one in five Americans, or 20 percent.
For the study, 36 dyslexic adults and 29 without the disorder were tested individually in a dark room in front of a video monitor. The participants pushed buttons to indicate which of two lights -- one a little higher, one a little lower -- appeared first.
Dyslexics and non-dyslexics alike had trouble performing that task when the lights were lit close together in time, Wallace says. But when the lights were accompanied by a hissing sound played over headphones, performance improved.
Non-dyslexics did better when the sound was played within roughly 150 milliseconds of the light -- but not longer. But the people with dyslexia showed benefits with delays as long as 350 milliseconds.
That delay in combining information from different senses goes to the heart of the problem dyslexic children experience when they are learning to read, the Wake Forest team reasons. Early reading is a multi-sensory process of matching words you see with words you hear or sound out. In dyslexics, that process is disrupted.
The study bolsters a teaching approach known as Orton-Gillingham, which relies on a combination of sight and sound to help dyslexics to read, write and spell, the researchers say.
Gordon Sherman, executive director of the Newgrange School and Educational Outreach Center in Princeton, N.J., is a proponent of that multi-sensory teaching method. He calls the Wake Forest research "a nice illustration of the importance of using both visual cues and auditory cues."
Thomas Viall, executive director of the International Dyslexia Association in Baltimore, adds that the new study is "probably good news" for parents of dyslexic children because it supports a multi-sensory education approach.
Viall says he always cautions parents to be careful when someone uses the word "cure" or promises a speedy fix for a child's dyslexia.
Wallace and his colleagues aren't promising any cures. But they do intend to perform further tests using magnetic resonance imaging to get a better handle on the mechanics of the disorder.
"The hope is that we'll be able to see what's different about the brains of dyslexics as opposed to normal-reading individuals," Wallace says. "Understanding the differences in the brain architecture may ultimately lead to a way in which we can change that architecture."
More information
To learn more about dyslexia, visit the Dyslexia Research Institute and the International Dyslexia Association.
