The brains of people with dyslexia, a learning disability characterized by difficulty in reading, are fundamentally different from those of normal readers, a study has found.
The study, presented at a recent meeting of the American Academy of Neurology, is based on a comparison of brain structures in 29 people with dyslexia and 21 normal readers. Researchers at the University of Miami School of Medicine used magnetic-resonance imaging, a technique that uses low-frequency radio waves and a powerful magnet, to produce brain images.
In the dyslectics, the neurologists found, the rear portion of the left half of the brain was either smaller than the corresponding part of the right half or the two halves were exactly the same size. That part of the brain was larger in normal readers.
They also found the corpus callosum--the band of nerve fibers connecting both brain halves-- was larger in the dyslectics than in the control group.
The researchers said the study, funded by the National Institute on Child Health and Human Development, offers clues to the cause of the disability, which affects an estimated 1 million schoolchildren. But they warned against using the same technique to diagnose dyslexia.
A provocative study by a University of California at Berkeley researcher suggests that boys taking Ritalin, a stimulant used to treat attention deficit- hyperactivity disorder, may be more likely to cheat and less likely to steal than others with the disorder who do not use the drug.
The unexpected findings stem from a continuing study of the drug by Stephen P. Hinshaw, an associate professor of psychology. He observed 44 boys ages 6 to 12, half of whom have the disorder. Of those with the disorder, half were taking Ritalin.
Each of the boys was led into a room planted with desirable objects, such as money, toy cars, and baseball cards. He was then asked to take a test that, if completed successfully, would bring a reward. The experimenter then left the room.
Of the boys with no disorder, 18 percent stole more than $1 when left alone. Among the beys with the disorder but not taking the drug, 45 percent stole that much; for Ritalin users, the incidence of theft was 41 percent.
Cheating on the test occurred among a quarter of the control group, compared with 39 percent of the Ritalin users and 31 percent of the boys with the disorder who were not taking the drug.
Mr. Hinshaw attributed the differences in stealing among boys with the disorder to the drugs success at centrolling impulsivity, but he said the findings on cheating were hard to explain.
He said the findings showed the need to use the drug only as part of a comprehensive program of therapy and behavior management.--D.V.
