2/13/2024 0 Comments Dyslexia and hearing"Adaptation is just one of the things that helps take the load off."īut reading is a different story. "The brain devotes a lot of infrastructure to solving these problems, and has multiple routes," says Perrachione. The systems that perform this processing are likely very robust. Perrachione and Gabrieli speculate that dyslexics don't struggle with processing of heard speech or seen objects and faces because human brains evolved to process these inputs. "In people without dyslexia, we always see adaptation, but in the dyslexics, the lack of adaptation was often really pronounced." "I am surprised by the magnitude of the difference," says Perrachione. Overall, the study involved over 150 individuals, and dyslexics on average had adaptation levels about half those of typical readers. They repeated this experiment with yet another group of individuals, this time focusing on children aged 6 to 9 with and without dyslexia. "This suggests that adaptation deficits in dyslexia are general, across the whole brain," says Perrachione. The reduced adaptation was observed in the regions of the brain responsible for processing the stimuli in question. Again they saw much less adaptation in participants with dyslexia. They recruited another group of individuals with and without dyslexia and examined adaptation to images of written words, faces, and objects, either in a series of different images or repeated images. So Perrachione and Gabrieli decided to look at adaption to visual stimuli, too. "If you were to talk to someone on the street, you'd have no idea if they were dyslexic or not," says Perrachione. These results raised questions, since difficulty understanding speech is not seen in dyslexia. "We saw much less adaptation in those with dyslexia group compared to typical readers." "Brains typically tune in and figure out what is consistent about a voice," says Perrachione. Dyslexics with better reading skills showed greater adaptation levels. But for dyslexics, brain activity remained high in both cases, suggesting that they did not adapt as much. Individuals without dyslexia adapted to a consistent voice and not to multiple voices. As brains adapt, the fMRI measures of brain activity in relevant brain areas drop. In some cases, the same voice spoke a series of words in others, different voices spoke each word.īrains typically adapt to a single, consistent voice within a second or two, but they don't adapt to many different voices. ![]() ![]() The researchers used functional magnetic resonance imaging (fMRI) to examine the brains of adults with and without dyslexia as they listened to voices. They zoomed in on the process of rapid neural adaptation. ![]() "Part of the mystery of dyslexia is that the brain doesn't have an area that evolved for reading," says Gabrieli. Working in the lab of lead investigator John Gabrieli, professor of Brain and Cognitive Science at MIT, he decided to investigate early, fundamental processes in the brain that could make this association difficult. Perrachione, who has a background in linguistics, wanted to investigate the theory that reading difficulties in dyslexia come from difficulties in associating sounds with written words. "Dyslexics are not getting this advantage." "Adaptation is something the brain does to help make hard tasks easier," says first author Tyler Perrachione, assistant professor of Speech, Language and Hearing Sciences at Boston University, who completed this research as a graduate student and post-doctoral fellow at MIT. The difference may explain some of the challenges people with dyslexia experience, such as discerning speech in a noisy environment and learning to read.
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