ROBERT SIEGEL, host:

From NPR News, this is ALL THINGS CONSIDERED. I'm Robert Siegel.

Children who have trouble reading usually do a lot better if they receive intensive instruction. And now, scientists have discovered one reason why.

As NPR's Jon Hamilton reports, a new study shows that intensive reading programs produce measurable changes in the structure of a child's brain.

JON HAMILTON: Reading involves a lot of different parts of the brain. Some recognize letters, others apply knowledge about vocabulary and syntax and still others decide what it all means. Somehow, the brain has to synchronize all these operations.

Marcel Just, who directs the Center for Cognitive Brain Imaging at Carnegie Mellon University, says that requires a really good communication system.

Mr. MARCEL JUST (Director, Center for Cognitive Brain Imaging, Carnegie Mellon University): You need these sort of high-speed - I don't know what to call them - highways between brain areas to let the information flow back and forth extremely effectively.

HAMILTON: If those information highways can't handle the traffic, the brain won't be able to make sense out of the text. Just wondered whether this might be part of the problem for a lot of children struggling to read.

So he and a colleague named Timothy Keller used a special type of MRI to look at the brains of several dozen poor readers as young as eight. The team focused on the network of fibers that carries information around the brain. That's a kind of brain tissue called white matter.

Mr. JUST: Tim Keller and I scanned these children and found that there was an area of white matter that was of lower structural quality than in the control group.

HAMILTON: The control group being kids with typical reading skills. During the next school year, some of the poor readers were enrolled in programs that provided a total of 100 hours of intensive, remedial instruction.

Mr. JUST: These children were really practicing how to read words, how to sound out words and read sentences over and over and over again, and that repeated remediation training is what changed not just their reading, the but changed the tissues in their brain.

HAMILTON: A second round of MRI scans showed that the quality of white matter had improved in the same areas found to be lacking before the kids got intensive instruction, just as there was no change among children in standard classes. And he says:

Mr. JUST: The amount of improvement in the white matter in an individual was correlated with that individual's improvement in his reading ability.

HAMILTON: The finding adds to the evidence that learning involves more than just gray matter, the brain tissues that process and store information.

Doug Fields works in the Child Health and Human Development section at the National Institutes of Health. He says the realization that white matter is also important for learning has led to a shift in the way many scientists view the brain.

Mr. DOUG FIELDS (Researcher, Child Health and Human Development, National Institutes of Health): By analogy we were looking at a transistor. And now we're looking at the whole network, like the Internet, and realizing for this whole network to operate, you need to have an efficient flow of information.

HAMILTON: Fields says other studies have shown that white matter also changes when people learn to juggle or play a musical instrument. And, he says, white matter seems to be involved in a wide range of brain function and dysfunction.

Mr. FIELDS: Psychiatric illnesses, mathematical ability, IQ. Really, the more we look, the more we find.

HAMILTON: Marcel Just says there's even evidence linking autism to problems with white matter and a lack of synchrony in the brain. The new study appears in the journal, Neuron.

Jon Hamilton, NPR News.

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