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Imaging study shows little difference between poor readers with low IQ and poor readers with high IQ

Last year, Fumiko Hoeft, MD, PhD, authored a study that used sophisticated brain imaging to predict with 90 percent accuracy which teenagers with dyslexia would improve their reading skills over time. Now the Stanford imaging expert has turned her attention to the diagnosis of the learning disability, and she and colleagues have provided “biological evidence that IQ should not be emphasized in the diagnosis of reading abilities."

As I explain today in a release, schools and psychologists sometimes rely on a child’s IQ to define and diagnose dyslexia: If a child's reading achievement is below expectation based on IQ, he would be considered dyslexic, while a poor reader with a low IQ would receive some other diagnosis. (And those children not considered dyslexic might not be given access to the proper reading interventions.) But in an imaging study of 131 children - including poor readers with typical IQ, poor readers with low IQ and typical readers with typical IQ - Hoeft and colleagues show that what happened in the brains of poor readers during a reading task was similar regardless of IQ:

In the fMRI analysis, researchers found that both groups of poor readers exhibited significantly reduced activations relative to typical readers in the left inferior parietal lobule and left fusiform gyrus. The researchers also used a sophisticated analysis to determine that the brain patterns of each group of poor readers looked liked those of the other group of poor readers more than 80 percent of the time, and did not often resemble the patterns from the normal readers.

The researchers said that their work, which will appear in an upcoming issue of Psychological Science, indicates that “any child with a reading difficulty, regardless of his or her general level of cognitive abilities (IQ), should be encouraged to seek reading intervention.” And:

Hoeft noted that the results are timely. The Diagnostic and Statistical Manual of Mental Disorders, the standard diagnostic guide for mental illnesses and brain disorders, is currently being revised, and there is a proposal to change it so that IQ wouldn’t be taken into consideration when diagnosing dyslexia. (The new version, DSM V, will be released in 2013.) This work, she said, is the “first study reporting biological neuroimaging evidence to support” that change.

Previously: Stanford study furthers understanding of reading disorders and Researchers use brain imaging to predict which dyslexics will learn to read
Photo by Marc Samson

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