A Magnetoencephalography Investigation of the Role of Stuttering Anticipation on the Preparation and Execution of Speech in Adults who Stutter

Coordination of the speech neural network in developmentally stuttering adults prior to initiation of individual speech utterances has not been explored. The objectives of this study were a) to characterize sensory-motor recruitment in preparation for and execution of speech in adults who stutter (AWS) using magneto-encephalography, and b) to investigate the effect of stuttering anticipation on such sensory-motor recruitment. Brain neural oscillatory activity was recorded during a cued overt repetition task. No differences between high and low anticipation were found. However, AWS demonstrate stronger bilateral recruitment of the mouth motor cortex compared to controls in speech preparation and execution. AWS also recruit the right mouth motor cortex before the left, while controls show a preference for the left mouth motor cortex. The study was the first to find differences in motor recruitment during speech in AWS. This is proposed to reflect facilitative mechanisms adopted in a limited motor speech network.M.Sc

Sensorimotor oscillations prior to speech onset reflect altered motor networks in adults who stutter

Adults who stutter (AWS) have demonstrated atypical coordination of motor and sensory regions during speech production. Yet little is known of the speech-motor network in AWS in the brief time window preceding audible speech onset. The purpose of the current study was to characterize neural oscillations in the speech-motor network during preparation for and execution of overt speech production in AWS using magnetoencephalography (MEG). Twelve AWS and twelve age-matched controls were presented with 220 words, each word embedded in a carrier phrase. Controls were presented with the same word list as their matched AWS participant. Neural oscillatory activity was localized using minimum-variance beamforming during two time periods of interest: speech preparation (prior to speech onset) and speech execution (following speech onset). Compared to controls, AWS showed stronger beta (15-25Hz) suppression in the speech preparation stage, followed by stronger beta synchronization in the bilateral mouth motor cortex. AWS also recruited the right mouth motor cortex significantly earlier in the speech preparation stage compared to controls. Exaggerated motor preparation is discussed in the context of reduced coordination in the speech-motor network of AWS. It is further proposed that exaggerated beta synchronization may reflect a more strongly inhibited motor system that requires a stronger beta suppression to disengage prior to speech initiation. These novel findings highlight critical differences in the speech-motor network of AWS that occur prior to speech onset and emphasize the need to investigate further the speech-motor assembly in the stuttering population