High-definition tDCS Treatment for Cantonese-speaking Adults Who Stutter

Using High-definition Transcranial Direct Current Stimulation to Improve Speech Fluency in Cantonese-speaking Adults Who Stutter - A Preliminary Investigation

The proposed study aims to investigate the effect of combined transcranial direct current stimulation (tDCS) and behavioural speech training in improving speech fluency in Cantonese-speaking adults who stutter (AWS), and to examine its maintenance over a 6-week period.

The proposed study aims to

1. assess the effect of multiple sessions of tDCS over the supplementary motor area (SMA) combined with behavioural speech training on stuttering recovery in terms of a reduction of stuttering severity and increased speech satisfaction in Cantonese-speaking AWS;
2. investigate the maintenance of combined tDCS-behavioural speech training effects on speech fluency and speech satisfaction in Cantonese-speaking AWS over a 6-week period.

Twenty Cantonese-speaking AWS will be randomly assigned to an experimental group and a control group. Both groups will receive behavioral treatment for stuttering, including the speech prolongation technique, for five sessions. Concurrent with behavioural training, the experimental group will receive anodal tDCS (1 mA for 20 minutes), while the control group will receive sham tDCS (1 mA for one minute), over the SMA. Stuttering severity and speech satisfaction will be assessed independently before, immediately after, one week and six weeks after treatment. It is anticipated that AWS will experience reduction in their stuttering severity after stimulation, and the improvement will be maintained for a longer period as compared with receiving behavioural treatment alone.

Inclusion Criteria:

• Demonstrated features of stuttering;
• More than 2% of syllables stuttered over three baseline speech samples, as measured by qualified speech therapists.

Exclusion Criteria:

• Personal or family history of epilepsy or seizures
• History of a neurological condition
• Speech disorders
• Hearing impairment
• Metallic foreign body implant
• On medications that lower neural thresholds (e.g. tricyclines, antidepressants, neuroleptic agents, etc.)
• Pregnant
• Had speech therapy for stuttering in the past four months