Scientists Explore Potential Neurological Cause of Dyslexia

Scientists have identified a "neural signature" of sorts in people with dyslexia that could explain why those who have the condition find it harder to interpret information.

According to Science Alert, brain scans have revealed that people with dyslexia tend to have to try twice as hard to process sensory information such as images and words.

Cognitive scientist John Gabrieli from MIT said it's not just about a difference in reading per se, but a difference in perceptual learning. This is a path by which a brain difference could influence learning to read, which involves so many demands on plasticity.

This is called neural adaptation, and works by the senses working together to analyze and interpret situations. 

For instance, a lot of people may see a picture of blobs that will eventually make out to be a dog sniffing the ground. When this information is clarified, looking back will not make everything see like a mass of blobs but instead the actual dog.

Gabrieli explained this is because we learn something upon the initial presentation that makes it easier to do it the second time, and the ease is marked by reduced neural activity. This is because it's something we've done before, so it's easier to do again.

However, according to the researchers, this almost-effortless brain activity that many of us don't realize is happening is much harder for people with dyslexia.In order to figure this out, the team analyzed the brains of young adults with dyslexia and those without the condition. This is so they could see how they responded to a series of sensory input tests.

The first experiment had people pair spoken words with images on the screen, and they did it twice. The first session had the words spoken by a single voice, and the second session had the words spoken by different voices.

The scans showed the people sans dyslexia adjusted quickly to the singular voice after an initial period of neural adaptation activity in the superior temporal gyrus, which processes speech and sound.

The test with multiple speakers had the area flare with new activity.However, for participants with dyslexia, this phase never eased off during the test. This indicates that the brains had to keep working hard to focus on processing the information from the single sensory input. 

However, the difficulty in understanding speech is not something usually associated with dyslexia.

On another test, they showed participants a stream of visual images, some of which were different and others repeated in the experiment.

The participants with dyslexia showed reduced adaptation to the repeated imagery, with the same neural signature of extra brain activity being involved to process the stimuli.

The brain location changed depending on the nature of the content that was being perceived but the reduced adaptation was consistent on different domains, suggesting that adaptation deficits in dyslexia are general and across the whole brain.

This means it may be because that written comprehension is a demanding activity that calls upon so many parts of the brain that leads to the impairment usually being discovered when children are having difficulty with reading.