The Effects of Single-Session Cathodal and Bihemispheric tDCS on Fluency in Stuttering
Developmental stuttering is a fluency disorder that affects many aspects of a person’s life. Recent transcranial direct current stimulation (tDCS) studies have shown promise to improve fluency when paired with fluency enhancing conditions. To date, bihemispheric tDCS has not been investigated in people who stutter, although several studies associated it with improved speech and articulation skills in aphasic patients. In this study, we aimed to investigate the effects of single-session bihemispheric and unihemispheric cathodal tDCS on fluency in adults who stutter. We predicted that bihemispheric tDCS with anodal stimulation to the left IFG and cathodal stimulation to the right IFG would improve fluency better than the sham and cathodal tDCS to the 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 intervention sessions. Three tDCS interventions were administered: bihemispheric tDCS with anodal stimulation to the left IFG and cathodal stimulation to the right IFG, unihemispheric tDCS with cathodal stimulation to the right IFG, and sham stimulation. Speech fluency during reading and conversation was assessed before, immediately after, and one week after each intervention session. There was no significant fluency improvement in conversation for any tDCS interventions. Reading fluency improved following both bihemispheric and cathodal tDCS interventions. 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.