Electrical stimulation of the brain may improve phonemic processing in dyslexia

Among adults with dyslexia, phonemic processing and reading accuracy can be improved by non-invasive electrical stimulation of the brain, according to new research in PLOS Biology.

The study, conducted by a research team from the University of Geneva, involved 15 adult participants with dyslexia and 15 healthy participants who underwent transcranial alternating current stimulation (tACS) over the left auditory cortex. The tACS sessions lasted for a span of 20 minutes.

In people with dyslexia, the phonological deficit of impaired processing of language sounds may be the cause of the disorder. In the new study, the intervention by use of tACS led to an improvement of phonological processing and reading accuracy among the dyslexic participants.

According to researchers, the participants with dyslexia experienced beneficial effects when stimulation reached 30 Hz. The stimulation led to improvements particularly among those with poor reading skills and slight paradoxical effects that occurred in avid readers without dyslexia.

“The intervention significantly improved phonological processing and reading accuracy as measured immediately after tACS. The effect occurred selectively for a 30-Hz stimulation in the dyslexia group,” Silvia Marchesotti, and her colleagues, determined in their findings.

“Importantly, we observed that the focal intervention over the left auditory cortex also decreased 30-Hz activity in the right superior temporal cortex, resulting in reinstating a left dominance for the oscillatory response,” they also determined.

“These findings establish a causal role of neural oscillations in phonological processing and offer solid neurophysiological grounds for a potential correction of low-gamma anomalies and for alleviating the phonological deficit in dyslexia.”

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