Bihemispheric and Cathodal Transcranial Direct Current Stimulation Improves Reading Fluency in Adults Who Stutter

In this study, we aimed to investigate the immediate effects of bihemispheric tDCS on fluency for adults who stutter and how the effects of unihemispheric cathodal tDCS montage differ from bihemispheric stimulation. We predicted that bihemispheric stimulation with anodal stimulation to left IFG and cathodal stimulation to the right IFG would improve fluency better than the sham and cathodal tDCS to right IFG. Seventeen adults who stutter completed this single-blind, crossover, sham-controlled tDCS experiment. All participants received 20 minutes of tDCS alongside metronome-timed speech during stimulation sessions. Speech fluency during reading and conversation was assessed before, after and, one week later each stimulation session. There was no significant fluency improvement in the conversation for any tDCS montages. Reading fluency improved after stimulation for both montages. When participants who were already fluent during pre-session reading evaluation excluded from analysis, only cathodal tDCS montage remained significant. TDCS montages were not significantly different in their effects on fluency. This study has significant implications in developing and applying interventions for people who stutter.