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Dartmouth College Office of Public Affairs • Press Release
Some dyslexic children can't read well because their brains don't properly process rapidly changing sound, according to a new study coauthored by a Dartmouth researcher. However, special training can help these children develop more normal brain responses and also improve as readers, the study shows.
These results are good news for dyslexic children and their parents, said neuroscientist Elise Temple, a Dartmouth assistant professor of education and the new study's senior author. "They can feel heartened by the evidence that the brains of dyslexics are really different. Kids can say to themselves, 'It's not my fault that I can't read—my brain works differently. I'm not lazy or stupid, it's just something biological.' On the other hand, our research shows that just because these differences are biological doesn't mean nothing can be done to change them. In fact, we've shown that certain measures can truly help."
The research is described in an article titled "Neural correlates of rapid auditory processing are disrupted in children with developmental dyslexia and ameliorated with training: An fMRI study," published Oct. 16 in an online edition of the journal Restorative Neurology and Neuroscience.
Words are composed of strings of sounds both relatively long and short in duration. The word "bad," for example, begins with the brief "b" sound followed by the longer vowel sound and then by the brief "d" sound. If you don't process brief sounds well, you may recognize the vowel sound but be confused about the consonant sounds. This confusion can make it harder to sort out letters and words as a reader, the researchers believe.
Although previous studies have found that dyslexic children have trouble discriminating between brief acoustic stimuli, this is the first to use functional magnetic resonance imaging (fMRI) to observe their brains' response to this stimulus. This diagnostic tool uses nuclear magnetic resonance to track changes in blood oxygenation, which in the brain denotes neural activity.
In the study, Temple and her colleagues performed whole-brain fMRI on 23 children with normal reading ability and 22 children with dyslexia, which is thought to affect between 5 to 17 percent of children.
The fMRI enabled the researchers to observe brain activity in response to short (six-tenths of a second) sound intervals in which the acoustic properties changed either rapidly (listen to audio clip)—over tenths of milliseconds, as in spoken words—or relatively slowly (listen to audio clip). They found that the brains of both normal readers and dyslexics responded similarly to the more slowly changing sounds. When more rapidly changing sounds occurred, however, activity stayed the same in the dyslexic children's brains-while activity in the normal readers' brains shifted to other areas, primarily the left prefrontal cortex, which underlies the left half of the forehead.
After the initial fMRI, the dyslexic children went through eight weeks of daily one-hour sessions of a dyslexia remediation program, Fast ForWord Language, designed by Scientific Learning Corporation of Oakland, Ca, which was founded by one of the study's coauthors, Paula Tallal, professor of neuroscience at Rutgers University. This program involves no reading and uses both nonverbal sounds as chirps and whistles as well as speech sounds in the form of syllables, words and sentences. Users must discriminate between paired sounds, such as choosing which one rose or dropped in pitch. The sounds change slowly at first and more rapidly as the program progresses.
Tested after the remediation program, the children showed brain activity much more like that of the normal-reading group. Better still, the children's reading scores as a group improved significantly, moving them into the low end of the normal range.
Although versatile and safe, fMRI is difficult to use with young subjects because it requires them to lie inside a dark capsule that makes loud, intermittent noises and to stay very still. More than 1 millimeter of motion spoils the image.
Temple was one of the first to successfully use the technology on children. Already a mother of two when she began graduate studies in neuroscience at Stanford University, Temple used what she says was "just common sense" to create a setting in which children would not only tolerate the fMRI but willingly come back multiple times.
Some of her winning practices are to limit the number of researchers who work with the children so as not to overwhelm them with strangers; let the children explore the equipment before settling down for the experiments; talk each child through the imaging to give instructions and warn about the noises; and reward the children for their cooperation at intervals throughout each session. Those rewards have included baseball or Pokemon cards—as well as a print-out of a view of their brain.
Along with Temple and Tallal, the study's authors are lead author Nadine Gaab, of the MIT Department of Brain and Cognitive Science and the Developmental Medicine Center at Children's Hospital Boston (see the Sound training rewires dyslexic children's brains for reading press release); J.D.E. Gabrieli of the MIT Department of Brain and Cognitive Science; and G.K. Deutsch of the Stanford Institute for Reading and Learning, Stanford University.
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