Faulty brain connections in adult dyslexia

It's been widely believed that adults with the reading/spelling difficulties often known as dyslexia have poor-quality representations of speech sounds in their brains.

Not being really clear about the differences between similar sounds (e.g. whether the third sound in "represent" is a "p" or a "b"), we've thought they were storing sounds in a weak or indistinct way.

New research from the University of Leuven in Belgium, however, suggests that the problem isn't with the representations themselves, it's with accessing them.

The University of Leuven was founded in 1425, and recently gave out honorary doctorates for poverty research, including one to Australian epidemiologist Fiona Stanley. So I am already predisposed to believe just about anything they say.

The lead researcher for this new dyslexia finding is Dr Bart Boets, who on YouTube looks like the excellent sort of young European you meet when you get up early to watch the sun rise from a remote temple in Guatemala, and end up sharing your snacks with them and some passing monkeys while admiring the view and solving a few of the world's problems. They all seem to have PhDs, speak five languages, think everyone's role in life is to make the world a better place, and Bart also wears no tie and has marvellous curly hair, he probably rides a bicycle, even when it's snowing. So now I'm very much inclined to believe anything he says, but will regroup, call him Dr Boets and try to stick to the facts from now on.

What's going wrong in adult dyslexic brains?

Dr Boets' research was trying to pin down what's going wrong in adult dyslexics' brains when they try to read and spell.

The research is entitled, "Intact but less accessible phonetic representations in adults with dyslexia". I'll link to his video describing it below, but he uses a lot of technical and medical jargon, so I'll give you an idea of what he says in plain English first.

Severe and persistent reading and spelling problems, or dyslexia, are very common. These difficulties run in families, and are related to how people's brains work.

Children learning to read and write in alphabetic languages like English and Dutch need to know what the sounds of their languages are, and learn the sound-letter relationships.

Robust and distinct phonetic representations

When we speak, we say each sound a little differently (depending on what other sounds are around it), but we have to build a robust and distinct concept of each sound before we can really make sense of how sounds are represented by letters.

For example, the sounds "b" and "d" are acoustically very similar, as they're made with a similar action (stop the air then let it go), both use voice, and they're not physically far apart (lips v/s tongue behind teeth). If you're not 100% sure which is which, it makes it hard to understand how they're written down.

Dr Boets' research first measured how well people's brains were representing sounds. They studied a group of 22 adults with dyslexia and a similar group of 23 adults without dyslexia, and compared how their brains lit up on brain scans (Functional Magnetic Resonance Imaging) when listening to different sounds.

They surprised everyone, including themselves, by finding that there wasn't much difference between the dyslexics and non-dyslexics. They both had intact, robust, distinct representations of sounds.

Accessing phonetic representations

The researchers scratched their heads and wondered whether the problem for people with dyslexia might be accessing these intact representations of sounds. It's all very well to have good representations, but not if you can't easily use them when you're trying to read and spell.

The brain is very complicated, but in general terms, our representations of sounds in words are stored in an area near the back of the ear on both sides of the brain (bilateral auditory cortices).

When reading, these areas need to communicate with other parts of the brain, especially the speech-language area further forward, in the left temple area, called Broca's area (left inferior frontal gyrus).

If you know someone who had a stroke and afterwards couldn't talk, they probably had damage to Broca's area. Broca's area doesn't store representations of sounds itself, so to process sounds for speech and language, it has to communicate well with the area that does store them.

The researchers found that the main difference between the dyslexics and non-dyslexics studied was in the connections between the areas that store representations of sounds and the areas that need to use them, especially Broca's area.

The people with dyslexia had impaired connections, both structurally (the nerves were different) and functionally (they worked less well).

One of the Psychology/Speech Pathology test areas in which people with persistent reading/spelling problems typically struggle is Rapid Automatic Naming (RAN), so perhaps Dr Boets' subjects had good early teaching/therapy regarding sounds and their corresponding spelling patterns, but it didn't resolve their RAN problems.

Practical implications

Humans don't have caterpillar-to-butterfly style transformations from child to teenager at 13, or from teenager to adult at 18, so this research is interesting to those of us who mostly work with children and teenagers.

Of course, others will need to repeat this research, with children, teenagers and adults, and find similar things, before too many sweeping conclusions are made about what it means.

A lot of teaching and therapy programs for dyslexia focus on strengthening the representations of sounds. This research suggests that, at least with adults, the focus should shift to strengthening access to these representations. That is, perhaps we should be focussing less on knowing, and more on doing.

I think my materials are useful in this regard, but only have clinical experience and others' feedback, not research data, as evidence. Maybe it's time to enrol in a PhD, wondering whether its results will be a surprise.

OK, now watch Dr Boets' video, and don't forget to admire his curly hair and imagine he has chocolate and beer for lunch (sorry, but I've never been to Belgium).

 

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