Dyslexics show a difference in sensory processing

Neuroscientists at MIT and Boston University have discovered that a basic mechanism underlying sensory perception is deficient in individuals with dyslexia, according to study published December 21 in Neuron. 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 for individuals with dyslexia, the researchers found that adaptation was on average about half that of those without the disorder.

But reading is a different story. It is a learned skill that requires multiple regions of the brain to work together, potentially with the harmony and complexity of a Rube Goldberg machine, says Perrachione. As rapid neural adaptation deficits simultaneously affect auditory and visual processing during reading, they may compound to make reading very difficult. "We have to see letters, map them onto words, map those to sounds, and connect them to semantics," says Perrachione. "There are lots of places for things to go wrong."

It isn't known yet exactly where things do go wrong as a result of deficits in rapid neural adaptation. "This study presents strong evidence for a foundational brain difference in dyslexia, but it isn't clear how to bridge that to the specific properties of reading," says Gabrieli. "It opens up as many questions as it answers."