Effect of transcranial direct current stimulation (tDCS) on tongue twister production : a preliminary study

Abstract

Previous studies have demonstrated beneficial effects of transcranial direct current stimulation (tDCS) on language and speech production in both healthy and aphasic individuals. In this study, the possible effect of anodal tDCS on speech production during reading aloud of Cantonese tongue twisters in healthy individuals was investigated. Fifteen healthy individuals were asked to read a list of tongue twisters before, immediately after and at least 4 hours after anodal tDCS (20 min, 2 mA) over the Broca’s area. Vocal reaction time, speech rate and response accuracy during tongue twister production were measured. Reduced vocal reaction time and increased speech rate were noted immediately after stimulation. These effects were found to be sustainable for at least 4 hours after the stimulation. No significant differences were observed in response accuracy among the three time points of measurements. The data revealed beneficial effects of anodal tDCS over the Broca’s area on speech production in reading aloud task. The findings are also in line with existing evidence, suggesting that the left frontal region is a critical region with potential therapeutic benefits of tDCS for patients with articulatory deficits.