Dyslexia: Major cause of learning difficulty may have been discovered by neuroscientists

‘Adaptation is something the brain does to help make hard tasks easier [but] dyslexics are not getting this advantage’

Ian Johnston
Science Correspondent
Wednesday 21 December 2016 18:03
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It's difficult for those without dyslexia to imagine what having it must be like
It's difficult for those without dyslexia to imagine what having it must be like

Scientists have discovered what appears to be a fundamental reason why people are dyslexic.

Using MRI scans to monitor the brains of people who present with the condition, and those who don’t, researchers found a “really pronounced” difference in responses to a series of visual and audio cues.

The brains of people without dyslexia were more able to recognise repeated words or images in a process known as “neural adaptation”, while a “neural signature” was identified among dyslexics, whose brains displayed lower levels of “plasticity” – or response ability.

The researchers were surprised to find such a broad range of effects but speculated that dyslexia only shows itself when people try to read because this is a relatively demanding task.

While humans have evolved to be skilled verbal communicators, writing is a relatively recent occurrence in our history, particularly as something that most people in society do.

One of the researchers, Professor John Gabrieli, of the Massachusetts Institute of Technology, said: “You learn something upon the initial presentation that makes you better able to do it the second time, and the ease is marked by reduced neural activity. Because you've done something before, it’s easier to do it again.”

Scans of the brains of people with dyslexia showed this adaptation process was not as effective – their brains were more exercised to understand the same information, the academics reported in the journal Neuron.

Speaking to The Independent, Professor Gabrieli said: “There are different ways to struggle to read, but for many individuals with dyslexia, we suspect this might be the route pathway – the beginning would be this broader reduction in [brain] plasticity that only manifests itself when the demands for plasticity are highest.”

He added the study suggested a potential new way to alleviate effects of dyslexia by artificially increasing the plasticity of the brain.

However Prof Gabrieli said the techniques used to do this – involving electromagnetic stimulation of the brain – were at an experimental stage and had not been tried for the condition.

“We’d love if it would have implications for helping people, but we know that’s far away,” he said.

Prof Tyler Perrachione, of Boston University – the lead author of the study – said: “Adaptation is something the brain does to help make hard tasks easier [but] dyslexics are not getting this advantage.

“I am surprised by the magnitude of the difference. In people without dyslexia, we always see adaptation, but in the dyslexics, the lack of adaptation was often really pronounced.”

About one in 10 people in the UK, some 6.3 million people, are estimated to have dyslexia.

In addition to making reading and spelling more difficult, it can affect short-term memory, maths and co-ordination. However it does not affect general intelligence or reasoning.

Dyslexia was first diagnosed in Seaford, Sussex, in 1896 as a “case of congenital word blindness” involving a 14-year-old boy called Percy.

A report in the British Medical Journal said that “in spite of this laborious and persistent training, he can only with difficulty spell out words of one syllable”.

“The schoolmaster who taught him for some years says that he would be the smartest lad in the school if the instruction were entirely oral,” it added.

However those with the condition were often dismissed as being “thick” or “lazy” and it was not until the 1970s that the role of language processing was recognised.

Professor Gabrieli said previous research had long laid that misconception to rest.

“I have colleagues who are professors who are dyslexic and who are amazing,” he said.

Dr John Rack, head of research at charity Dyslexia Action, said the researchers had come up with “some interesting findings”.

“What is particularly interesting is that better reading skills in adults and children with dyslexia were associated with greater repetition-induced neural adaptation,” he said.

“We also recognise that these results highlight a dysfunction of rapid neural adaptation as a core neurophysiological difference in dyslexia that may underlie impaired reading development and this new evidence is helping to build an understanding of the differences in brain functions which can ultimately result in a greater understanding of specific reading impairments.

“This is theoretically well-grounded research that is seeking to explain what we know to be the core issues for people with dyslexia: learning to map letters and sounds for the development of fluent reading and spelling skills. Increasing this understanding can help us to tailor our teaching interventions to be even more effective.”

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