Dyslexic People Have Differences In Part Of The Brain Related To Speech Adaptation

Dyslexic People Have Differences In Part Of The Brain Related To Speech Adaptation

People with dyslexia typically have difficulties with reading, writing, and spelling. While there are different levels of the condition, it is thought that up to 1 in every 10 to 20 people may have the problem to a degree. Now, researchers may have found differences in the brains between those who do have dyslexia, and those who don’t.

Dyslexia makes it difficult for people to recognize the different sounds that make up a word, and subsequently how these then relate to the words on a page. This latest study has found there is a difference in the region of the brain that is involved in how the brain rapidly adapts to sensory input, such as another person’s voice, or images of faces. Typically, this region helps to make the processing aspect more efficient, but in people with dyslexia this area of the brain was around half the size of those from the control group.

“Adaptation is something the brain does to help make hard tasks easier,” said Tyler Perrachione, lead author of the study investigating this link, published in Cell Press. “Dyslexics are not getting this advantage.”

By using functional magnetic resonance imaging (fMRI) scans of adults as they listened to voices, the researchers could investigate how the processing of these sounds varies between those with and those without dyslexia, as the brain adapts to different people talking.

The differences seen in the two groups when listening to changing voices. Perrachione et al. 2016

Obviously, however, dyslexia isn’t an auditory problem, but rather one of not being able to read correctly. So the researchers then repeated the experiments on those with the condition and a control group, this time getting them to look at images of written words, images, and objects. What they found was that, once again, there was far less adaptation in those with dyslexia.

“This suggests that adaptation deficits in dyslexia are general, across the whole brain,” explained Perrachione. It turned out that on average, dyslexics had adaptation levels to both visual and auditory stimuli of around half that of those who did not have dyslexia, a much larger difference than the researchers were expecting.

They speculate that the reason we don’t see dyslexic people having issues with recognizing speech or faces on a day-to-day basis is because the processes behind these are very ancient and hardwired in the brain. But with reading, the story is different. Reading is a relatively new behavior for humans, and is a learned skill using multiple parts of the brain, including the adaptation parts assessed in the study. It could be that because reading is using all these parts simultaneously, the processes get mixed up for some people.