Dyslexics show a difference in sensory processing
In 2016 Neuroscientists discovered that a basic mechanism underlying sensory perception is deficient in individuals with dyslexia. 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.
“Dysfunction of Rapid Neural Adaptation in Dyslexia” by Tyler K. Perrachione, Stephanie N. Del Tufo, Rebecca Winter, Jack Murtagh, Abigail Cyr, Patricia Chang, Kelly Halverson, Satrajit S. Ghosh, Joanna A. Christodoulou, and John D.E. Gabrieli was published in Neuron online December 21 2016 doi:10.1016/j.neuron.2016.11.020
Another study by Jaffe-Dax, Frenkel & Ahissar was published in 2017 in eLife, 6, e20557. http://doi.org/10.7554/eLife.20557 ; “Dyslexics’ faster decay of implicit memory for sounds and words is manifested in their shorter neural adaptation”.
Dyslexia is a reading disability, although why it happens is still not understood. In the 2017 study, they studied if neural mechanisms underlying dyslexia could be explored using a simple frequency-discrimination task. Participants were asked to compare two tones in each trial – and the study was devised to explore if implicit memory of previous trials affected their responses. They had hypothesized that implicit memory decays faster among dyslexics.
People with dyslexia showed a faster decay of implicit memory effects. They discovered that faster decay of implicit memory also characterised the impact of sound regularities in benefitting dyslexics’ oral reading rate. The study suggests that people with dyslexia had a shorter neural adaptation, with is in contrast to their longer reading times. They hypothesised this is because it reduces their temporal window of integration of past stimuli, resulting in noisier and less reliable predictions for both simple and complex stimuli.