Sept. 8 (UPI) -- Electrical stimulation of the brain improves reading accuracy in adults with dyslexia, according to a study published Tuesday by PLOS Biology.
Transcranial alternating current stimulation, a non-invasive procedure that delivers low-dose electricity to the brain over a period of 20 minutes, was found to improve phonological processing -- or ability to discern how words sound or are pronounced -- and reading accuracy in 15 adults with dyslexia, the researchers said.
The beneficial effect on phonological processing was most pronounced in those individuals who had poor reading skills, while a slightly disruptive effect was observed in very good readers, they said.
Dyslexia, known commonly as a reading disorder, affects up to 10% of the population, and is characterized by lifelong difficulties with written material," according to the researchers, who are from the University of Geneva in Switzerland.
Although several possible causes have been proposed for dyslexia, the predominant one is a phonological deficit, or a difficulty in processing word sounds, the researchers said.
The phonological deficit in dyslexia is associated with changes in rhythmic or repetitive patterns of electrical activity in the brain, specifically "low-gamma" oscillations, measuring at 30 hertz or volts, in the left auditory cortex, they said.
However, studies have yet to prove that these these oscillations affect a person's ability to process word sounds and cause dyslexia, the researchers said.
For this study, the researchers applied transcranial alternating current stimulation over the left auditory cortex in 15 adults with dyslexia and 15 fluent readers for 20 minutes.
At a dose of 30 hertz or volts, the approach resulted in significant improvement in reading accuracy in those with dyslexia, the researchers said.
However, the same improvements were not seen following application of a higher, 60-hertz dose, they said.
The results demonstrate for the first time that low-gamma oscillatory activity causes deficits in phonemic processing and may pave the way to non-invasive treatments aimed at normalizing oscillatory function in auditory cortex in people with dyslexia, the researchers said.
They plan "to investigate whether normalizing oscillatory function in very young children could have a long-lasting effect on the organization of the reading system [and] explore even less invasive means of correcting oscillatory activity," study co-author Silvia Marchesotti, a post-doctural researcher at the University of Geneva, said in a press release.