Effects of transcranial direct current stimulation over the Broca's area on tongue twister production

Abstract

Purpose: The present study aimed to explore the short-term effect of anodal transcranial direct current stimulation (tDCS) on tongue twister production. Method: Thirty healthy native Cantonese adult speakers were randomly assigned to the anodal tDCS group or the sham tDCS group. Anodal tDCS of 2 mA was applied over the Broca’s area of the brain. The stimulation lasted for 20 min for the anodal tDCS group and 30 s for the sham tDCS group. The participants were instructed to produce a list of tongue twisters before, immediately after and 4 h after tDCS. Result: Speech rate and response accuracy measured immediately after stimulation were significantly faster and higher, respectively, than before stimulation. Although there was no change in speech rate measured at 4 h after stimulation, response accuracy at that time point was significantly lower than that measured immediately after stimulation. However, there were no significant differences between the anodal tDCS and sham tDCS groups in either speech rate or response accuracy. Conclusion: The findings revealed that a single session of anodal tDCS over the Broca’s area did not significantly improve speech production during tongue twister production.