A systematic review of transcranial magnetic and direct current stimulation application on the improvement of reading ability of developmental dyslexia

Abstract

Transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS), two non-invasive brain stimulation techniques (NIBS), are modulatory tools to probe into a possible causal and interaction relationship between brain structure and function. Developmental dyslexia (DD) is a neurodevelopmental disorder, which is characterized by significant and persistent difficulty in learning and reading-related skills. Previous studies have shown that TMS and tDCS play an important role in reading ability and neurocognitive plasticity, such as visuospatial working memory, attention, speech recognition, and motor perception. However, research on the effectiveness of TMS/tDCS in treating DD is still limited. The current study aimed to systematically review the broadly application of TMS/tDCS in the treatment of dyslexic children and adolescents as well as adults. Twelve studies involving 128 dyslexic subjects (199 children/adolescents and 29 adults) were included in this systematic review. Overall, TMS/tDCS appeared to be an effective technique for treating dyslexia. However, further future studies with larger sample sizes as well as more different languages are essential to demonstrate its potential for successful intervention in DD. This systematic review suggested that the combination of tDCS and cognitive training was effective. Moreover, the treatment with multiple sessions and coupled with behavioral training appeared to result in greater efficacy than stand-alone NIBS treatment.