Bihemispheric Transcranial Direct Current Stimulation* on Speech Fluency

Developmental stuttering is a fluency disorder that can negatively affect many aspects of an individual's life. Recent transcranial direct current stimulation (tDCS) studies with individuals with stuttering show that tDCS shows promise in increasing fluency when used in combination with situations that temporarily increase fluency. In this study, it was aimed to investigate the effect of bi-hemispheric tDCS on fluency in individuals with stuttering for 5 consecutive days. The hypothesis of the study is that bi-hemispheric stimulation, which includes anodal stimulation to the left hemisphere and cathodal stimulation to the right hemisphere, will be effective on reading and speech fluency when performed for 5 consecutive days. Thirty-six adults with developmental stuttering are expected to complete this double-blind, sham-controlled study. Participants will be divided into two groups by blocked randomization and one group will receive sham stimulation for 5 consecutive days and the other group will receive bihemispheric stimulation. Participants in the tDCS group will receive 20 minutes of tDCS stimulation accompanied by metronome-timed speech during the practice sessions. Reading and speaking fluency will be assessed immediately before, immediately after, and one week after the stimulation sessions. Data will be collected using the stuttering severity assessment instrument (SSI-4) Results will be compared both within and between groups in terms of percentage of stuttered syllables, stuttering severity, and evaluation of the speaker's experience of stuttering.