Investigating Non-invasive Brain Stimulation to Enhance Fluency in People Who Stutter

Reading, narrative, and conversational speech tasks will be completed on each of the five intervention days. Metronome- timed speech will be practiced during these tasks, at near-normal (comfortable) speech rate for each participant. Each intervention session will be 40 minutes in duration.

1-mA tDCS with the anode (5 x 7 cm) placed over the left frontal cortex and the cathode (5 x 7 cm) placed symmetrically over the right frontal cortex. tDCS will be delivered using a direct current (DC) stimulator in 'study-mode' for 20 minutes. The current is ramped up to 1 mA over the first 15 seconds of stimulation and maintained at this level for remainder of the 20-minute stimulation session.

Sham stimulation will be delivered using a DC-stimulator in 'study-mode' for 20 minutes. Participants will receive sham stimulation with the anode and cathode electrodes placed over the left and right frontal cortex as in the active arm. For sham stimulation, the current is ramped up over 15 seconds, maintained for 15 seconds at 1 mA and ramped down over 15 seconds at the start of stimulation and is then followed by brief (3ms) pulses every 55 seconds for the remainder of the 20-minute stimulation session.