Dyslexia may be more than a reading disorder: Study

New York: A distinctive neural signature found in the brains of people with dyslexia may explain why they have difficulty in learning to read and adapting to sensory inputs, according to a new study.

The brain typically adapts rapidly to sensory input, such as the sound of a person's voice or images of faces and objects, as a way to make processing more efficient. 

But, the study found that for individuals with dyslexia, the adaptation was on average nearly half.

In dyslexic people, the brain has a diminished ability to acclimate to a repeated input -- a trait known as neural adaptation. 

For example, when dyslexic students see the same word repeatedly, brain regions involved in reading do not show the same adaptation seen in typical readers.

This suggests that the brain's plasticity, which underpins its ability to learn new things, is reduced, said John Gabrieli, professor at Massachusetts Institute of Technology (MIT) in the US.

"It's a difference in the brain that's not about reading per se, but it's a difference in perceptual learning that's pretty broad," Gabrieli added.

For the study, the team used MRI technique where the brains of young adults with and without reading difficulties were scanned as they listened to a series of words read by either four different speakers or a single speaker.

The results revealed that the dyslexic participants showed much less adaptation to hearing words said by a single speaker.

Further, for dyslexics the brain activity remained high while listening to a consistent voice and not to multiple voices, suggesting that they did not adapt as much. 

Again, when researchers looked at adaptation to visual stimuli, they saw much less adaptation in participants with dyslexia.

"This suggests that adaptation deficits in dyslexia are general, across the whole brain," noted Tyler Perrachione, assistant professor at Boston University in Massachusetts, US. 

The study appears in the journal Neuron.