ARTICLE IN BRIEF
Investigators found that the volume of white matter in an area of the brain that governs the use of language was increased following a six-month daily reading program.
Training poor readers to get better at sounding out words and comprehending what they read seems to have an unexpected benefit: a physical change in brain structure and not just function, according to a new study in the Dec. 10 Neuron.
Scientists from Carnegie Mellon in Pittsburgh, PA, found that the volume of white matter in an area of the brain that governs the use of language was increased following a six-month daily reading program.
Other studies have used imaging during a specific task to show that discrete areas of the brain are underactive in people with specific cognitive or motor deficits, including poor readers; past research has also shown white matter deficits in poor readers compared to good readers.
But, said Marcel A. Just, PhD, who conducted the study with Tim A. Keller, PhD: “This is the first evidence for an increase in white matter in response to a remedial behavioral intervention. It provides evidence that repeated cognitive exercises can alter cortical connectivity of the human brain.”
Dr. Just, professor of psychology at Carnegie Mellon and director of the Center for Cognitive Brain Imaging, said the findings open a window into fixing faulty wiring in other neurological conditions.
Thomas Insel, MD, director of the National Institute of Mental Health, agrees. “The evidence is mounting that the brain is wired to fix itself in so many ways,” he said. “This elegant study bridges the divide between psychology and biology in showing how the brain responds to a cognitive challenge. This study is on reading, but it is just a matter of time before other scanning studies show that psychological interventions alter the biology of our brains.”
STUDY PROTOCOLS, RESULTS
Dr. Just and his colleagues took MRI scans of 47 children between 8 and 10 years old with poor word decoding skills compared with 25 age-matched volunteers with no reading problems. The group differences were obvious to the trained eye: Those with reading problems had decreased microstructural organization of the white matter in a region of the left frontal lobe.
Most poor readers (35 of the 47) received daily remedial training for six months and the rest (12 of the 47) did not have any reading intervention. At the end of the training period, the children had another MRI, which showed that “instruction resulted in a change in white matter in the very same region that showed deficiencies in white matter before the intervention,” according to Dr. Just.
Changes on the brain scan correlated with improvement on some of the reading measures, he added. Specifically, the children were better able to sound out words, which resulted in an easier time reading.
Diffusion tensor imaging (DTI) taken right after the intervention revealed no white matter differences between poor readers and good readers. “And the location of the change is the same as where we first observed the deficit,” Dr. Just said. “We were surprised too. The amount of change in white matter was equal to the change in the child's reading ability, specifically in sounding out words.”
There were no changes in the white matter in the poor readers who did not receive remediation training. “This suggests that it is not a matter of development but of the intervention itself,” Dr. Just said.
INTERVENTION, BRAIN CHANGES
The question is how it works. Dr. Just speculated that as the children use these circuits over and over again, oligodendrocytes that construct the white matter are building up more myelin along the axons being fired. This myelin-rich insulation around the fibers makes the neural signal travel 10 times faster and delivers a more precise signal, he added.
Dr. Just said that DTI scans show the signal was less diffuse moving outwards from the center of the fibers. The result is that instead of drifting outward the signal is going straight along the fiber tracks. In theory, this more direct signal is stronger.
There is growing evidence that the brain does change in response to training. In a 2005 study in Nature Neuroscience, Swedish scientist Sara L. Bengtsson, PhD, used DTI to examine the effects of piano practice on white matter in childhood, adolescence, and adulthood. She reported that musicians who spent extensive time practicing piano had a richer store of white matter in response to thousands of hours of practice. But these studies did not include before and after practice scans or information about the extent of the structural change.
The Carnegie Mellon psychologists have brought some of the once-poor readers in for another round of scanning more than a year after the remedial training. There is no evidence that white matter continued to grow beyond the normal levels seen at the end of the intervention. In other words, too much learning is not bad for the brain, Dr. Just added.
That behavioral strategies can improve brain connectivity suggests that such interventions could be used to strengthen neural signals in people with autism, stroke, traumatic brain injury and even conditions like multiple sclerosis where myelin sheath is damaged.
“Although the basic computing power of the brain surely lies in individual neurons, it is only their collective action, made possible by white matter connectivity, that enables the multi-centered large-scale brain networks that characterize human thought,” the scientists wrote in the Neuron paper. “For this reason, modest modifications in white matter may enable major changes in cognitive ability.”
As for the once poor readers, they are now four years older and on a better footing in their reading lives. “Anecdotally, parents are delighted with the results of the program. Their children are reading more and enjoying it,” said Dr. Just.
Dr. Insel, of the NIMH, said that he hopes that the advances in imaging will soon be put to the test in showing the benefits of behavioral or other forms of psychological therapy in re-organizing cerebral architecture and altering its function. “This is a great place to be,” said Dr. Insel. “We now have the tools to understand how cognitive strategies alter the biology of the brain.”