Impaired connections between the brain’s auditory and speech centers may cause dyslexia, according to a study recently published in Science.
Bart Boets, a clinical psychologist at the Catholic University of Leuven in Belgium, led a team that studied brain scans of 23 dyslexic college-age adults and 22 college-age adults with normal reading skills. They discovered that the phonetic part of language were intact in adults with dyslexia — but likely less accessible because of brain connectivity deficits.
“For a long time it was thought that in dyslexics the data on the server are somehow degraded,” Boets told the Los Angeles Times, likening the human brain to a computer. “Yet, here we show that the quality of the data is intact, but the connection to reach this data is too slow.”
Study participants heard a sequence of four partial words, then another sequence in which a consonant or vowel had been switched, such as “ba-ba-ba-ba” to “da-da-da-da.” The participants were then asked to describe what changed.
Advanced functional magnetic resonance imaging (fMRI) techniques measured the brain’s response and found it was identical for dyslexics and normal readers.
Though their brains were identifying the sounds and the changes correctly, the dyslexic test subjects took 50 percent longer to respond, according to Science.
Researchers also examined how well the brain’s 13 studied areas communicated with each other and measured synchronized low-frequency activity. In both cases, the signals indicated that functional connectivity was normal between auditory cortex hemispheres.
Boets said the results were surprising because his team expected to reach difference conclusions. Scientists have theorized for more than 40 years that dyslexia is tied to defects in the brain’s “phonetic representations,” which is how the brain categorizes basic sounds.
The debate in science has been whether those with dyslexia were accurately forming and storing distinct units of sound or whether impeded access hindered the process of synthesizing sounds with written, visual symbols.
As children learn to read, their brains connect written symbols and spoken word components. But people with dyslexia seem to struggle to make that connection, resulting in reading and spelling difficulties.
Scientists estimate that more than 10 percent of the world’s population may have dyslexia, according to livescience.com
Understanding dyslexia’s roots may enable scientists to discover better ways to help those with the malady. Traditional therapies have centered on the strengthening of phonetic representations.
Boets suggested the results could help develop more-refined therapies that attempt to zero in on specific brain connections. He speculated that non-invasive magnetic stimulation of certain brain areas is a possibility.
“These fMRI studies have helped us improve interventions for children,” Ben Shifrin, vice president of the International Dyslexia Association and also head of the Jemicy School in Baltimore, which specializes in teaching children with language-based learning disorders, told Newsday.
For example, Shifrin said more hours per day of instruction is important in making progress.
