Using functional magnetic resonance imaging (fMRI), researchers led by a husband-and-wife team at Yale have found a neuronal short circuit in dyslexic children and identified an area of the brain that is linked to skilled reading. Their finding builds on a previous study that linked poor reading in adults with dyslexia to a specific region in the brain. “Because this finding coincides with findings in adults, it shows dyslexia is persistent,” said Sally E. Shaywitz, M.D., professor of pediatrics with an appointment in the Child Study Center and co-author of the study. “It shows there is an urgency for early intervention. And we were able to identify an area of the brain that correlates with skilled reading, the word-form area in the back of the left side of the brain.”
Shaywitz and her husband, Bennett A. Shaywitz, M.D., professor of pediatrics and neurology with an appointment in the Child Study Center, found that neural circuits in the word-form area, also known as the occipito-temporal area, are disrupted in children with dyslexia.
“By seeing the disruption on brain imaging it says to us as physicians and scientists that dyslexia is as real an entity as any other medical disorder,” said Bennett Shaywitz, co-principal investigator of the study and lead author of the paper in the July 15 issue of Biological Psychiatry. Also contributing to the work was John C. Gore, Ph.D., now at Vanderbilt University.
This study follows one in 1998 in which the Shaywitzes and colleagues found a disruption in posterior neural systems for reading in the brains of dyslexic adults. That finding begged a key question. “We did not know if this disruption was just the end result of years of poor reading or if it was there from the beginning of the time a child should be able to read, which is around 6 or 7 years old,” said Sally Shaywitz.
The team used fMRI to scan the brains of 70 dyslexic readers and 74 nonimpaired readers ages 7 to 18 while they performed reading tasks with real words and “pseudowords,” made-up words that the children were asked to pronounce. The tasks mimicked the problems dyslexic children face in sounding out words. The team found evidence of a functional disruption of the neural systems involved in skilled reading, confirming the hypothesis that the defect is present at a young age.
“We believe dyslexic children are born with this disruption,” Bennett Shaywitz said.
The nature and cause of the disruption are not clear. “That’s the next step,” he said. With colleagues at Yale, he’s using magnetic resonance spectroscopy to study brain cells in the region that is disrupted.
According to the Shaywitzes, about one in five children has dyslexia, which affects children without regard to level of intelligence. Typically, dyslexics compensate by using other parts of the brain to read.
“Instead of being able to develop systems in the back of the brain they develop systems in the front of the brain, but it is very laborious,” said Sally Shaywitz. “It’s not that they don’t learn to read at all, but it’s harder to read.”
Although symptoms appear as soon as children start to read, most dyslexic children are not diagnosed until they’re in the third grade, she said. “There is absolutely no question that the earlier a child is identified, the more difference you can make,” she said, adding that early placement in preventive and remedial programs can help children with dyslexia. The programs use exercises, games and rhymes to help dyslexic children break up words into their individual parts. “If you start at the beginning you can have a good chance of helping that child in an efficient way. What we think—and we have some evidence to support this—is that we can help the area of the brain that is disrupted.”