Parents often tell their children to sound out the words as they are learning to read. It makes sense: Since they already know how to speak, the sound of a word might serve as a clue to its meaning.
It turns out there’s a surprising and deep connection between what’s going on in your mouth and how your brain handles reading, and a University of Alberta research team hopes to use it to help people with dyslexia and other reading difficulties.
In a new study with the alliterative title Perturbing the pathway: The impact of lollipops and lidocaine on supramarginal gyrus activity during silent reading tasks, the team found that numbing the mouth can help people read faster.
They carried out the study on just 30 adults and there’s a lot more work to be done, but it points to a mouth-brain connection that may hold the key for future treatments.
“Our research is definitely bridging a gap between a couple areas of research that are often overlooking one another even though they are so tightly coupled,” says first author Mitchell Holmes, a PhD candidate in the Faculty of Rehabilitation Medicine. “It will help inform the importance of considering speech mechanisms in helping people learn how to read, especially people who struggle with reading.”
Study participants — all proficient readers — were asked to carry out two separate reading tasks while their brains were monitored for activity in the neighbouring regions that handle reading and speech.
“We wanted to see how disruptions to the sensory areas in the mouth while reading could affect performance,” Holmes explains. “We know already that when you’re reading a new word, your mouth sends information to the sensory parts of your brain. If it detects incongruencies with how that word should sound or feel, it will send a corrective command to the motor parts of your brain to tell it how to correct it and say it better on your next attempt.”
For the first task, participants were shown a string of letters and asked whether they spelled a real word or not — pressing green for yes and red for no. The second task asked whether a string of letters sounded like a real word. So “bloo,” for example, would be a yes, even though that isn’t how “blue” is really spelled.
Each participant went through the tasks three times under different conditions, first with nothing in their mouth, then with a large lollipop on their tongue and finally, after a swish of lidocaine to numb their mouth. The researchers looked at accuracy and reaction time to assess reading performance.
Results showed that the lidocaine helped some of the participants read faster, but still accurately. It also reduced activity in the sensory part of the brain, while the lollipop increased activity there.
“Taken together, these preliminary and modest effects suggest that oral somatosensory input influences reading-related brain activity and inter-regional connectivity,” says Holmes. “It’s a subtle effect, so we don’t know how these effects generalize to other reading tasks or populations. That’s something we want to explore more.”
The next step for Holmes’ research will be to carry out similar, more detailed studies on people who have dyslexia, which affects between five and 10 per cent of the population, according to Dyslexia Canada. The results may mean that speech-language pathologists could play a greater role in helping people with reading difficulties, Holmes says.
“The importance of somatosensory feedback in reading definitely warrants more targeted exploration to better our understanding of the relationship between speech-motor processes and reading ability,” he says.
The research was funded in part by a Natural Sciences and Engineering Research Council of Canada research grant to Holmes’ PhD supervisor, Jacqueline Cummine. Cummine is a professor in the Department of Communication Sciences and Disorders, Canada Research Chair in the Neuroscience of Literacy and a member of the Women and Children’s Health Research Institute.