Electrical stimulation of a sound-processing area of the brain can briefly improve reading skills in adults with dyslexia, a new, small study has found.
Researchers say their results suggest that deficits in that brain region are a cause of the reading difficulties seen in dyslexia.
But whether that's the case -- or whether brain stimulation can help treat dyslexia -- remains an open question.
The study, of 30 adults with and without dyslexia, looked at the effects of electrically stimulating a brain area called the left auditory cortex. Altered activity in that brain region has been linked to the difficulty people with dyslexia have in processing the sounds of language.
What's been unclear is whether that brain difference actually causes problems with processing language sounds, according to lead researcher Silvia Marchesotti, of the University of Geneva in Switzerland.
Her team found evidence that it does. When study participants were given 20 minutes of electrical pulses to the left auditory cortex, it immediately improved reading accuracy in those with dyslexia.
The effect was short-lived, disappearing an hour later. But the findings lay the groundwork for exploring whether noninvasively "normalizing" activity in the auditory cortex can help treat dyslexia, Marchesotti said.
Dyslexia is a learning disability that affects up to 15% to 20% of Americans, according to the International Dyslexia Association. It causes difficulty with reading, as well as other language skills like spelling and writing.
It's a common misperception that dyslexia is a visual issue, said Tyler Perrachione, an associate professor of speech, language and hearing sciences at Boston University.
Instead, he explained, people with dyslexia have deficits in processing the sounds that make up language -- which is a key element in learning to read.
Reading is such an ordinary part of life, it can be taken for granted. But it is actually a complex skill, involving the orchestration of various brain domains, said Perrachione, who was not involved in the new study.
Other research has shown that the brain looks and functions differently in numerous ways in people with dyslexia, versus those with typical reading skills.
Scientists are still unsure exactly how things are going awry, according to Perrachione. But there may be problems in the connections between the sound-processing part of the brain and other areas involved in reading -- such as those that interpret the meaning of language or govern the visual part of reading.
Perrachione said the new study takes "a promising approach" to understanding the underpinnings of dyslexia. But he cautioned that it does not necessarily offer proof of a direct cause of the disorder.
And whether electrical stimulation of the brain can help treat dyslexia remains to be seen.
The effects of one round are short-lived, Perrachione pointed out. And he said he doubted that electrical stimulation alone would be helpful.
But one possibility, Perrachione said, is to test it in combination with specialized reading instruction -- the standard way to manage dyslexia.
Such research might largely focus on adults. "Researchers are rightly conservative when it comes to brain stimulation in children," Perrachione said.
The current study, published Sept. 8 in PLOS Biology, included 15 adults with dyslexia and 15 with typical reading skills. Using electroencephalography, the researchers found that people with dyslexia, as expected, had certain abnormal activity patterns in the left auditory cortex.
Participants underwent 20 minutes of a technique called transcranial alternate current stimulation, where electrodes placed on the scalp deliver electrical pulses to the brain.
Immediately afterward, volunteers with dyslexia showed an improvement in their reading accuracy, but not speed. In contrast, the stimulation seemed to have a "slightly disruptive" effect on strong readers, the researchers said.
In a journal news release, Marchesotti said her team plans to study the possibility of "normalizing" activity in the left auditory cortex of young children with dyslexia. And that, she said, could potentially be done with even less invasive means, like neurofeedback training. That involves using sensors to monitor brainwave activity as people perform a task.
The International Dyslexia Association has an overview of dyslexia.