Researchers believe dyslexia is linked to "neural pegs" that work to categorize sounds so they can be effectively interpreted.
About 10 percent of the global population struggles with dyslexia, a condition that makes it hard to "read and process" words, a KU Leuven news release reported.
Researchers have been unsure of what causes dyslexia, and have been arguing over its roots for 40 years. Some believe the dyslexic brain distorts phonetic representations while others think it has to do with the region of the brain responsible for language interpretation.
"The two hypotheses are very difficult to disentangle," Bart Boets, a clinical psychologist and postdoctoral research fellow at KU Leuven, said. "This is because cognitive [behavioral] tasks always tap both the representation and the access to this representation simultaneously. Therefore, we needed neuroimaging to tease the two apart and assess them in isolation.""
The researchers scanned the brains of 22 participants with regular brain function 23 dyslexic subjects using functional magnetic resonance imaging (fMRI). The team monitored brain activity while the participants were listening to "speech sounds made of vowels and consonants."
"I was so convinced that we would observe degraded (i.e., less robust and distinct) phonetic representations in the dyslexic participants," Boets said. "Yet, their representations turned out to be perfectly intact."
The researchers observed phonetic representations were on point with the dyslexic individuals. They looked at how well 13 regions of the brain linked to language interpretation responded in both groups of participants and how easily they connected to observed phonetic representation regions. They found the worse the connection between these brain regions the more severe the condition.
"A finding from the functional connectivity analysis that I think is pretty striking," Boets said. "is that "decreased connectivity is found specifically between the very same superior temporal regions found to support intact phonetic representations in the MVPA analysis."
The team concluded "deficient access" to phonetic representations was related to dyslexia as opposed to the quality of these representations.
"It was by combining and applying two different analysis techniques on the same data set that we were able to draw these controversial conclusions," Boets said, explaining the leap forward that he and his group could make.
The team hopes to keep working to confirm their finding.
"With this new knowledge, it is not unconceivable that we could design more focused and effective interventions that specifically target improving the specific connection between frontal and temporal language regions," Boets said.
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