An electromyographic examination of lip asymmetry during speech and non-speech oral movements in adults who stutter

Past research investigating stuttering has cited atypical cerebral lateralization in adults who stutter (AWS) during speech production. The purpose of this study was to measure cerebral activation in AWS as indicated by lip asymmetry. The study included five AWS (mean age = 26 years of age) and five adults who do not stutter (AWNS) (mean age = 25 years of age). The tasks included single-word productions, single-sentence readings and lip pursings. The peak electromyographic (EMG) amplitude was determined for the left upper, right upper, left lower and right lower lip quadrants around the mouth. Overall, EMG amplitudes were higher for the lower lip than the upper lip. Based on examination of peak EMG amplitude, significant differences were found between speaker groups. For both speech and non-speech tasks, the highest EMG amplitude for the AWS and AWNS groups were on the left lower and right lower sides of the mouth, respectively. The AWNS group showed strong correlations in EMG activity across the four lip sites (r>0.97), indicating an overall synchronous lip activity during speech and non-speech tasks. In contrast, the AWS group showed a strong correlation (r=0.97) only for the left upper and left lower lips while the other lip pairings were not strongly correlated (r