Electrical stimulation of the brain can help people who stutter science

When Guillermo Mejias was 7 years old, his parents sent him to buy bread during a family vacation in southern Spain. Mejias still remembers his growing anxiety as he walked to the bakery, repeating what he would say over and over in his head. But when the time came, he could not utter a word. He remembers returning empty-handed, embarrassed and wondering what to say to his parents. “I was so tense that I inadvertently bit my cheeks and tongue and my mouth was bleeding,” he said.

Mejias is still stuttering, but today, as a brain researcher at Complutense University in Madrid, he is exploring ways to treat the problem. He is part of a growing group of researchers who rely on non-invasive brain stimulation, a set of techniques that apply small electrical currents to specific areas of the brain. A few years ago, Mejias tested such a technique on himself in a one-time experiment that temporarily reduced the frequency of his stuttering, he said. Several randomized trials, including one published this month in Journal of Fluency Disorders, also suggest that brain stimulation may be beneficial for people who stutter. “I think brain stimulation is the future,” says Mejias.

Not everyone agrees. No study has yet reported effects lasting months after treatment, let alone years. And anecdotal evidence suggests that attempts to treat stuttering are susceptible to the placebo effect, which means that only after participating in the study can participants see positive effects that are not due to treatment.

It is estimated that about 1% of the world’s adult population – about 70 million people – stutters, which can worsen quality of life and cause social stress and stigma. But the reasons for this are still poorly understood.

The only treatment available, speech therapy, can improve fluency to some extent and help avoid the side effects of stuttering, such as involuntary movements and tics. But the success rate is limited in adults and fails to address the root of the problem, says Mejias: “Treating stuttering with speech therapy is similar to treating Parkinson’s disease with physiotherapy.

However, non-invasive brain stimulation directly stimulates or inhibits neurons in specific brain regions in an attempt to remodel chains of interconnected cells. It has already shown benefits in depression – especially in people who are resistant to medication – and in rehabilitation for stroke, where it can help improve movement and speech.

Mejias and others tested its effects on stuttering using various techniques to apply electrical stimulation to speech circuits. Participants can then perform a task that reactivates these same regions, such as reading text in unison with another person or with a metronome, which many people who stutter can do with some degree of fluency.

The hypothesis is that performing these tasks after stimulation can help reshape problem chains. Although electric currents can cause mild discomfort, non-invasive brain stimulation is considered safe.

For his doctorate, Mehias studied the effects of a technique called transcranial magnetic stimulation (TMS), in which a magnetic field is applied through a small coil placed on a participant’s head, causing a small electric current to the brain. The coil is only a few millimeters wide, which allows the stimulation to be directed to precise areas of the brain. Mejias focuses on the extra motor area, an area of ​​the cerebral cortex involved in movement control that indicates abnormal functioning in people who stutter.

Because the study was largely exploratory – and to avoid the bureaucracy of a bigger test – Mehias decided to test TMS on himself. In a short article published in 2019, he reported that the treatment reduced blocks and repetitions in his speech by 30%. “I felt a progressive improvement, which also helped me build my confidence,” he said. “The effects were obvious for a few weeks, but we didn’t see them consistently, so I don’t know exactly how long they lasted.

Kate Watkins, a neuropsychologist at Oxford University, was the first to treat stutterers with another technique called transcranial DC stimulation (tDCS), which transmits electrical current from one side of the brain to the other. Because the electrodes used in tDCS are relatively large, researchers have less control over where stimulation occurs than with TMS, but the equipment needed is much simpler and cheaper. “If it works, it’s something that speech and language pathologists can use very easily and safely,” says Watkins. Another advantage: It often causes less discomfort than TMS.

In a randomized, double-blind study of 30 participants published in 2018, Watkins and colleagues applied direct current for 20 minutes for five consecutive days. They aimed to stimulate the left lower anterior cortex, a brain area involved in language and speech processing that shows reduced activity in people who stutter. To control the placebo effect, half of the participants received a false stimulation with minimal current – enough to feel something, but too weak to cause an effect.

The benefit is statistically significant, but modest: After 1 week, participants who received brain stimulation stuttered 8% of their syllables, from 11% at baseline, with no noticeable changes in the control group. The study, published this month by researchers in Iran, Germany and Canada, involved 50 participants and was similar in both design and outcome, with syllable stuttering falling from 8.5% to 5.4% after stimulation.

“The results of the improvement are obvious and similar in both,” said Julio Prieto, head of the clinical neurophysiology department at the Gregorio Maranhón University General Hospital in Madrid, who is also studying stuttering and working with Mejias. “From my point of view, both have the same limitations,” he added: several treatment sessions and a short follow-up period, making it impossible to say whether the effect was lasting.

Prieto says the district will benefit from more standardized protocols. Like many non-invasive brain stimulation studies, stuttering experiments differ in design and equipment. The experiments also target different brain regions and use currents of varying intensity and duration. “And there are factors you can’t control, such as gender differences, participant vigilance, and even genetic variation,” Prieto said. Several studies have shown that there is great variability in responses to brain stimulation between individuals.

Dennis Draina, an honorary geneticist at the U.S. National Institutes of Health who works on stuttering, says skepticism is okay. “Dozens of different treatments for stuttering have been tried, often with great initial success,” he said. “None of them lasted.”

Researchers at brain stimulation hope to convince skeptics. Mejias is looking for funding to expand his own experiment into a larger study. Watkins and her team plan to try another type of electrical stimulation called transcranial AC stimulation, in which the amplitude of the current is not fixed but oscillates. “It mimics natural brain rhythms,” said Birtan Demirel, a researcher at Watkins’ lab who also stutters.

Mehias is optimistic about treating stuttering at its roots. “The brain was almost mythical, no one knew how it worked. We are now beginning to understand it and we will be able to modify it in the future. “

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