Study Finds Distinctive Brain Patterns in People With Dyslexia
Findings on dyslexia reported last week add new elements to the complex puzzle over why it is more difficult for some people to learn to read, but researchers cautioned that potential solutions to the problem are still a long way off.
The study, supported by the National Institute of Child Health and Human Development, used advanced imaging technology to identify specific patterns of brain activity, or a "neural signature," among people with dyslexia.
Though such technology has been used for years in dyslexia research, the latest study, published in the March 3 issue of the Proceedings of the National Academy of Sciences, was the first to look at functions in the whole brain at once, according to NICHD officials. The study was also the first to use noninvasive techniques--it did not require the injection of radioactive dyes into the brain. The technique can now be used to study children.
People with dyslexia have trouble breaking spoken words into their component sounds and with matching the letter sounds to the letters they represent. The condition effects some 10 million Americans. ("Dealing With Dyslexia," Nov. 12, 1997.)
The study, led by Dr. Sally E. Shaywitz and Dr. Bennett A. Shaywitz of the Yale University school of medicine, compared the brain activity of 29 dyslexic readers with that of 32 normal readers.
Brain Patterns Identified
The researchers used functional magnetic resonance imaging, which produces computer-generated images of the brain while the subject performs various reading tasks. Images of the brains of the dyslexic readers showed a pattern of activity different from that of normal readers in the areas of the brain that link visual functions and language.
The pattern provides a neural signature for the learning disability, according to Sally Shaywitz, the study's lead author.
"If you have a broken arm, we can see that on an X-ray," Dr. Shaywitz said. "These brain-activation patterns now provide ... evidence for what has previously been a hidden disability."
G. Reid Lyon, the chief of the NICHD's child-development and behavior branch, said the study builds on the findings of earlier research.
"In many cases, people always had a difficulty trusting dyslexia as a difficulty that has roots in biology," he said. "This is one of many studies that clearly indicate that the reading difficulty is clearly associated with a difference in brain activation in areas that handle components of reading."
Researchers note, however, that any practical application of the results could be years away.
"At the moment it is just another scrap of evidence," said Frank R. Vellutino, a professor of psychology at the University at Albany, State University of New York. "We are still far from the point where it can inform classroom teachers."
A companion study on children is being conducted by the Yale group in conjunction with researchers at Syracuse University in Syracuse, N.Y. Preliminary results are expected later this year.