THURSDAY, June 6 (HealthDay News) -- A new brain imaging study
appears to rule out one potential cause of dyslexia, finding that
vision problems don't lead to the common reading disorder.
The new research could have a wide-ranging impact on the
detection and treatment of dyslexia, said senior study author
Guinevere Eden, director of the Center for the Study of Learning at
Georgetown University Medical Center. The study appears June 6 in
"It has importance from a practical viewpoint. It means you shouldn't focus on the visual system as a way to diagnose dyslexia or treat dyslexia," Eden said. "Until now, there was still this uncertainty where some people were saying, 'I know it's controversial but I still believe that vision is contributing to these kids' reading problem.' We now have a finding that really speaks to an understanding that visual system function shouldn't have a role in diagnosis or treatment."
People with dyslexia struggle to learn to read fluently and
accurately. Dyslexia may affect more than one of every 10 people in
the United States, and it is the nation's most common learning
disability, according to background information in the study.
Earlier brain imaging studies have found that people with
dyslexia experience subtle weaknesses in processing visual stimuli
compared with people their same age, leading some to wonder whether
this visual dysfunction causes dyslexia by interfering with a
child's ability to read.
But the study found that visual problems noted in people with
dyslexia likely are a result of the learning disorder rather than
the cause, Eden said.
By ruling out the visual center as a culprit, the new study
provides more support to the already popular theory that dyslexia
occurs because of weaknesses in the part of the brain that deals
with language, she said.
Researchers used functional MRIs to compare the brains of
dyslexic children with the brains of children who don't have the
Children without dyslexia appeared to have the same level of
visual processing activity as dyslexic kids, when matched by
reading level instead of age, they found.
Further, children with dyslexia who received intensive tutoring
in reading skills experienced a subsequent increase in visual
"When we ask children to learn to read, we are asking them to do something that is very difficult. Learning to read changes the brain," Eden said. "If you are a struggling reader because of your dyslexia, you don't have as much opportunity to read as the other kid in your class, and so your brain doesn't get the chance to change as much. The visual deficit is there, but our study allowed us to conclude it's there as a consequence of not having the same opportunity to read as children without dyslexia."
The new paper represents a key step forward for the field in
that it narrows down the potential causes of dyslexia and helps
shape future detection and treatment, said Laurie Cutting,
associate professor of special education, psychology and radiology
for the Peabody College of Education and Human Development at
Vanderbilt University in Nashville, Tenn.
"Vision issues or involvement of visual processing have been reported and talked about for a long time with dyslexia, but so have issues involving language," Cutting said. "This paper begins to reconcile why these two types of findings exist, and provides some clues as to the future investigation of causal mechanisms."
Cutting said future research should focus on replicating these
findings, and providing further explanation for the interplay
between the visual and language centers of the brain.
"There's still the question of why this is a consequence of dyslexia," Cutting said of the visual impairments.
Eden said the new study also can be applied more broadly to
other disorders in which differences in brain activity have been
"We always have this chicken-and-egg problem," she said. "When we see a difference in a brain scan, we say, 'Was it there from the beginning and caused the problem, or is it the end product of an already existing problem?' In this case, consider that we've only been actively teaching children to read in the last 100 years. You are asking your brain to do something it wasn't designed to do, and having to do it induces all kinds of changes in the brain."
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