Mismatch occurs between seeing letter and the sound it represents, study suggests
New brain scans reveal more about how the minds of people with dyslexia work.
The key problem seems to be a mismatch between seeing the letter and connecting it to the sound it represents or vice-versa, said researchers from the University of Maastricht in the Netherlands.
In addition to enhancing basic knowledge of this learning disability, the researchers hope the findings will lead to more effective interventions for the problem.
“This study contributes to understanding how the brains of dyslexic readers might process the relation between print and speech differently than non-impaired readers,” said study author Vera Blau, a doctoral student in psychology. “Although it is clearly too early to translate these results into practical applications, these insights could be used to validate existing training strategies for dyslexia or perhaps contribute to understanding the nature of the neural changes that are driven by effective intervention.”
The findings, published in the March 12 online issue of Current Biology, seem to be in line with previous research.
“It shows the basic neural network that we knew was going to be there,” said Dr. Kathryn J. Kotrla, chairwoman and an associate professor of psychiatry and behavioral science at Texas A&M Health Science Center College of Medicine and associate dean of the Health Science Center Round Rock campus. “The experiment laid the foundation for the neuro-anatomy of dyslexia versus the non-impaired reader.”
Some 4 percent to 10 percent of the population has dyslexia, a learning disorder which involves challenges with language skills, including reading, spelling, writing and pronunciation of words, according to the International Dyslexia Association (IDA).
Previous studies have shown differences in the way the brains of dyslexic individuals are “wired,” as compared with the brains of “normal” people. In particular, past research has also shown a disconnect between being able to identify the sounds within a word and matching them with the letters, according to the IDA.
The study involved 13 dyslexic readers and an equal number of “non-impaired” readers.
Volunteers were shown visual letters and listened to auditory speech sounds corresponding to single letters. The researchers conducted functional MRI while the participants performed a series of these experiments.
Dyslexic participants had less activation of the superior temporal cortex region of the brain which, among other things, is involved with processing sounds.
“They looked at what happens when people with and without dyslexia try to integrate visual representations with sound representations, and even though that’s been thought to be one of the areas that’s a problem, this is novel, because they have used brain imaging technology,” said Guinevere Eden, director of the Center for the Study of Learning at Georgetown University. “A typical person has an augmented response in this part of the brain, and in dyslexics, they’re not seeing that augmentation, suggesting that there does not seem to be a system in place to show that there’s an association [between visual and sound] that’s going on.”
“This is an important step, and it raises the potential for exploring the effects of clinical interventions and for investigating different subtypes of reading challenges,” Kotrla said. “There are a million different variants of how visual and auditory processing works.”