Dyslexia Studies Catch Neuroplasticity at Work


by Tom Valeo

November, 2008

Researchers using functional magnetic resonance imaging, or fMRI, have detected which parts of the brain become stronger as children with dyslexia develop their ability to read. As reported in the journal Neuropsychologia, follow-up scans one year after the children received 100 hours of remedial reading from teachers showed that this increase in activation continued, reaching normal levels in the left parietal lobe.

These fMRI scans reveal the vigor of neuroplasticity, the process by which neurons create new connections among themselves.

“What we demonstrate is that we can change the way the brain works,” says Marcel Just, director of the Center for Cognitive Brain Imaging at Carnegie Mellon, who conducted the research. “The study shows that we can make a brain area more active through remedial training.”

New connections among neurons preserve memories and make learning possible, but they also fortify brain functions. Research has shown that a pianist, for example, through practice, develops neural pathways in the motor cortex that make subtle finger movements possible. Blind people who read Braille actually expand the region of the somatosensory cortex devoted to processing input from their reading finger.

And children with dyslexia, according to Just’s findings, can strengthen connections in parts of the brain that enhance their ability to read. Teachers have long recognized that children with dyslexia can improve their reading ability, but imaging is just beginning to provide evidence of the changes in the brain that make this possible.

Nadine Gaab, an assistant professor of pediatrics at Children’s Hospital Boston, along with colleagues at the Massachusetts Institute of Technology, performed fMRI scans on 22 children with dyslexia and 23 normal readers, all about 10 years old, while they listened to typical speech sounds. She found that normal readers showed activation in the frontal lobe in response to rapid changes of sound, while children with dyslexia did not.

“We are currently using fMRI to look for neural pre-markers for reading,” Gaab says. “We hope we will be able to identify these markers prior to the onset of reading in order to identify children at risk.”

Gaab’s findings support research conducted by Paula Tallal, who, more than 35 years ago, identified dyslexia as a problem involving the processing of speech sounds.

“When you start to read, you have to learn how to go inside of a word and recognize smaller, faster units of sound,” says Tallal, a professor of neuroscience and psychiatry at Rutgers University.

Sally Shaywitz, director of the Yale Center for the Study of Learning and Attention, has used fMRI to compare brain activity in dyslexic children and in normal readers while they sound out nonsense words such as “jeat” and “lete.” The large differences she found constitute what she calls a “neurological signature” for dyslexia.

For example, she found that normal readers displayed greater activity on the left side of the brain, especially the parieto-temporal region—the same region that got stronger in the students Just studied after they worked with remedial reading teachers.

But dyslexia is not a problem confined to a single area of the brain, and explanations of the disorder implicate several brain functions.

In the 19th century, dyslexia was known as “word blindness,” a phrase that suggests visual difficulties as the cause. A small percentage of children with dyslexia do have problems seeing words. Deaf children with the disorder, for example, cannot hear phonemes—the one-syllable sounds that make up spoken words—which are believed to confuse dyslexic children with normal hearing, so their reading difficulties must be visual. And in 1982 physiologist John Stein of Oxford found that some children with dyslexia have trouble focusing on words and scanning text smoothly. Some researchers also suspect problems in the cerebellum, which might help explain the balance and coordination difficulties of some children with dyslexia.

But a rapidly growing body of research suggests that the vast majority of children with dyslexia have trouble distinguishing among phonemes. They may have trouble hearing the difference between “ba” and “pa,” for example, or “mif” and “tif.” While they can say “cat,” they may have trouble distinguishing the three phonemes that make up the word: “kuh,” “aah,” and “tuh.”

As a result, children with dyslexia have trouble with the fundamental task of reading, which involves translating letters on the page into phonemes and then building those phonemes into words.

Tallal has applied this hypothesis to develop effective, computer-based remedial reading programs. She also would like to see neuroplasticity used to improve memory, attention, processing speed and sequencing skills, which are vital to all learning.

“In our schools we’ve focused on improving the curriculum, the teachers and the medications we give children, but we’ve never focused on improving the brain the child brings to the classroom,” Tallal says. “That brain can be modified.”

And those modifications are not limited to children.

Ways of Changing the Brain

 Not so long ago, scientists viewed the brain as a form of concrete—soft and easily shaped in youth, but gradually hardening over the years into a rigid organ highly resistant to change.

A child’s brain certainly displays vigorous neuroplasticity. For example, children can absorb a foreign language far more easily than adults, and they can speak it without an accent if they start speaking it before their late teens.

But scientists now recognize that the brain remains surprisingly plastic and resilient throughout life, which creates opportunities for adults to make positive changes in their neural connections through focused attention and practice.

“Neurology, psychology, speech therapy, education, sports, music—all of these domains will be improved as we apply the laws of neuroplasticity,” says Norman Doidge, a faculty member at Columbia University’s Center for Psychoanalytic Training and Research and the University of Toronto’s Department of Psychiatry, and author of The Brain That Changes Itself.

Doidge presents many examples in his book of how neuroplasticity can change brain function dramatically. He interviews Edward Taub, for example, a behavioral neuroscientist at the University of Alabama who developed constraint-induced movement therapy to help stroke patients regain the use of a paralyzed arm. In the late 1970s Taub noticed that monkeys who lost sensation in one arm would stop using it unless their other arm was constrained. Then they would start using the numb arm again. The same technique, when applied to stroke patients, spurs their brains to “rewire” themselves and restore at least some function to the paralyzed arm.

Doidge also tells of a woman whose sense of balance was destroyed by an antibiotic, making it almost impossible for her to walk. She regained her balance, however, with the help of the late University of Wisconsin neuroscientist Paul Bach-y-Rita, who devised a helmet that sent signals about the orientation of her head to a device on her tongue. By learning to keep the signals centered on her tongue, the woman trained her brain to recognize when her head was upright.

Until now, the evidence attributing such dramatic changes to neuroplasticity has been largely circumstantial, but fMRI is producing vivid images that show neuroplasticity in action. In 2005, for example, Swedish investigators used diffusion tensor imaging—a variation of fMRI done with the same equipment—to demonstrate distinct brain changes caused by extensive piano practice.

And Just plans to investigate further the type of brain changes he observed in the dyslexic children he studied. He believes fMRI evidence of neuroplasticity can be used to diagnose dyslexia and other brain problems, and to test proposed therapies.

“We can use fMRI to evaluate educational approaches and see which ones are getting us to the desired brain end state,” says Just. “There were these endless phonics wars, for example. It was like debating how many angels can dance on the head of a pin. Now, with fMRI, you can see which methods work best. Plus you can see what kinds of problems with reading children are having, which would provide a better idea of how to remediate.”