Phonics Instruction Helps the Dyslexic Brain
Different Brain Patterns Seen in Those With Dyslexia
By Richard Saltus
Dyslexic people show an abnormal pattern of brain function when reading: underactivity in some regions, overactivity in another. And that accounts for the difficulty they have in extracting meaning from the printed word, researchers say.
The findings provide evidence that people with dyslexia are not poorly taught, lazy, or stupid, but have an inborn brain abnormality that has nothing to do with intelligence, say the scientists from Yale School of Medicine.
"I feel really very gratified that these individuals can now say there is good evidence that this is a neurobiological disorder," said Dr. Sally Shaywitz, a Yale pediatrician who headed the study. The evidence has been accumulating for a number of years. Dyslexia is believed to afflict 10 percent or more of all children.
Dyslexia is defined as a significant reading disability in people with normal intelligence.
The new picture of brain abnormalities was obtained by placing normal and reading-impaired volunteers inside computerized magnetic resonance imaging (MRI) scanners, then having them perform successively harder reading tasks.
Shaywitz said the study means "we've identified a system in the brain that allows us to go from looking at printed words to connecting it to the sound structure of words," and that dyslexics have "glitches" in the system.
Shaywitz said the poorly performing brain centers are ones that are crucial to what is called phonological processing, that is, the ability to discern the relationship between letters and letter groups and the spoken sounds they represent. People with dyslexia can learn these relationships with intense phonics training, but they have trouble doing it naturally.
Dyslexics have trouble breaking down unfamiliar words into letter-sound segments. As a result, reading is slow and filled with errors.
When normal readers were challenged with tasks of increasing difficulty, brain scans revealed greater and greater activity in crucial brain areas, the Yale team wrote in the current issue of the Proceedings of the National Academy of Sciences.
In dyslexic volunteers, the same brain centers in the rear part of the brain, centers that involve visual perceptions, failed to become more active in response to the phonological tasks, the authors said.
At the same time, a region in the front of the brain became overactive, as if trying in vain to compensate for the failure of the other areas, they said. This frontal region, said Shaywitz, enables an individual to convert visual information into sounds. It's been known that damage to this brain center can cause adults to lose the ability to read.
The Yale researchers tested 29 dyslexic volunteers and 32 nonimpaired volunteers and found significant differences between the two groups. Both groups were composed of men and women.
Paula Tallal, a neuroscientist at Rutgers University in Newark, NJ said the study "beautifully pulls together" recent findings about phonological processing difficulties in dyslexia. And, she said, it focuses on how important the phonics approach is in teaching dyslexic children to read.
Dr. Albert Galaburda, a neurologist at Beth Israel Deaconess Medical Center in Boston who has studied structural differences in the brains of dyslexics, said the findings clearly show the perceptual problems dyslexics have, but he called the study "a very pretty confirmation of things we already knew."
Turning on the Brain
Yale researchers have shown when people with dyslexia try to read, a front part of the brain is over-stimulated while crucial portions in the center and back are under-stimulated. The diagrams show brain stimulation during reading.
Source: Drs. Sally Shaywitz and Bennet Shaywitz
New York Times