Brain images show different pathway among those who overcome
 

07/14/2003

Newsday

Using MRI brain scans to pinpoint the pathway for reading, scientists at Yale were surprised to find two different brain circuits activated when people with dyslexia, or severe reading problems, read simple words. The research showed that dyslexic readers who overcome the problem do so by employing a different brain circuit than that used by both normal readers and dyslexic readers who fail to improve.The finding, which appears in this month's Biological Psychiatry, suggests that a large percentage of people with reading problems have a normal brain circuitry that doesn't seem to have been activated in time to learn the skills necessary to become proficient readers. Reading takes accuracy, understanding and fluency (speed).

This is the first biological evidence for two distinct brain patterns used by poor readers, according to Dr. Sally E. Shaywitz, a professor of pediatrics at Yale Medical School and lead author of the study. The researchers found that the major difference between two groups of poor readers – those who learned to compensate and became better readers and those who never did – was related to their school environment.

While at least a third of all the poor readers had a biological vulnerability that made reading difficult, the rest seemed to be affected by poor schooling. The better the education, the better the reading skill, the scientists found. The brain scans revealed that the persistently poor readers had "a working system, but it's never been properly activated," Dr. Shaywitz said. "This offers great hope that if they were to get high-grade instruction early enough, these kids might do very well."

In other words, for a large group of problem readers, it's more a matter of environment than biology itself.

Brain scientists have identified specific areas called on during reading. Scientists had identified significant disruption in the wiring of the brain's left posterior regions in people with dyslexia. Problem readers developed secondary systems in the left and right frontal lobes that enabled them to eventually overcome the problem. The brain compensated for the deficit and recruited other brain areas to carry out the task. But while their accuracy and comprehension improved, they never developed fluency, or speed.

Yale's 20-year exploration into the brains of readers from 5 to 25 now suggests that brain abnormalities are not the same in those who learn to overcome their reading handicap and those who don't.

Dr. Shaywitz and her colleagues have been following almost 500 children into adulthood, taking routine snapshots of their reading and academic life to better understand the making of a reader.

When these volunteers were in second grade, one in five showed severe reading impairments. By ninth grade, a third of these poor readers had improved. They weren't as fast as normal readers but they were accurate and they understood what they were reading. The other two-thirds of the poor readers continued to have problems.

Now that the volunteers are in their early 20s, the Yale researchers invited a hundred of them back to peer inside their brains. They were sent inside a functional magnetic resonance imaging device that takes a picture of the active brain. While in the scanning device they were shown nonsense words or real words and were asked to group them into categories.

While sounding out the phony words, those who seemed to compensate for their dyslexia and others who continued to struggle with reading both showed an underactivation of two brain areas linked to reading – the left parietal-temporal and occipital-temporal areas.

But it was during the second experiment when the differences emerged, said Dr. Shaywitz, author of Overcoming Dyslexia, published this year by Alfred A. Knopf. The volunteers were shown simple words and asked to categorize them. The persistently poor readers had the same brain pattern as those who never had problems reading, Dr. Shaywitz said.

By comparison, the young adults who by the ninth grade had called on other brain regions to become better at reading still showed deficits in the normal reading regions.

So what was going on? Dr. Shaywitz said the answer emerged when they looked back on all the data they collected. It seems that the persistently poor readers were more likely to have come from poorer schools and they were less verbal than their compensating counterparts.