Research study: "The application of neuronavigated rTMS of the supplementary motor area and rhythmic speech training for stuttering intervention" (2024, May)

Research study: "The application of neuronavigated rTMS of the supplementary motor area and rhythmic speech training for stuttering intervention" (2024, May) Open Access: [https://www.researchgate.net/publication/380374795\_The\_application\_of\_neuronavigated\_rTMS\_of\_the\_supplementary\_motor\_area\_and\_rhythmic\_speech\_training\_for\_stuttering\_intervention](https://www.researchgate.net/publication/380374795_The_application_of_neuronavigated_rTMS_of_the_supplementary_motor_area_and_rhythmic_speech_training_for_stuttering_intervention) ​ **Abstract:** Background Stuttering, a neurodevelopmental speech fluency disorder, is associated with intermittent disruptions of speech‐motor control. Behavioural treatments for adults who stutter (AWS) concentrate on adopting speech patterns that enhance fluency, such as speaking rhythmically or prolonging speech sounds. However, maintaining these treatment benefits can be challenging. Neuroimaging studies suggest that supplementary motor area (SMA) which play a crucial role in speech initiation, planning and internal timing shows aberrant activation in speech production of AWS and may contribute to stuttering. Preliminary evidence suggests that brain stimulation may impact responsiveness to behavioural treatments. Aims The present study aims to investigate whether excitatory repetitive transcranial magnetic stimulation (rTMS) of the SMA and rhythmic speech can consistently reduce stuttering severity across various measures. Methods and Procedures Ten self‐identified Cantonese‐speaking AWS participated in this double‐blinded, sham‐controlled clinical trial study (NCT 05472181). The participants underwent 10 sessions of rhythmic speech training across two phases, combined with either neuronavigated rTMS or sham, with a 2‐week washout period between phases. The stuttering severity was assessed through various outcome measures, including the percentage of syllables stuttered, self‐perceived stuttering severity, and the brief version of Unhelpful Thoughts and Beliefs About Stuttering before and after each treatment phase. Outcomes and Results Results demonstrated improved speech fluency in various speaking contexts, with no significant difference between rTMS and sham conditions immediately and 1 week post‐treatment. Notably, rTMS specifically led to less stuttering in tongue twister production ( d = –0.70). Both treatment conditions effectively reduced self‐perceived stuttering severity and negative thoughts and beliefs about stuttering. Conclusions and Implications The findings of this study indicate that stimulating the SMA reduced stuttering, only in the production of tongue twisters that may require greater motor control and coordination. Furthermore, it indicates that rhythmic speech might help alleviate negative beliefs and anxiety related to stuttering. This research contributes to our understanding of neuromodulation in stuttering treatment and the role of the SMA in speech motor control and emphasises the need for more research on the potential benefits and limitations of applying rTMS in this condition. WHAT THIS PAPER ADDS What is already known on the subject Behavioural treatments for adults who stutter concentrate on adopting speech patterns that enhance fluency, such as speaking rhythmically or prolonging speech sounds. However, maintaining these treatment benefits can be challenging. Neuroimaging studies indicate that aberrant neural activation in speech production regions, like the supplementary motor area (SMA), is involved in stuttering. The SMA plays a crucial role in initiating, planning, and sequencing motor behaviours. Preliminary evidence suggests that brain stimulation (e.g., transcranial direct current stimulation or transcranial magnetic stimulation) may impact responsiveness to behavioural treatments. What this paper adds to existing knowledge There is limited knowledge regarding the potential effects of stimulating the SMA to enhance speech fluency in people who stutter. Existing research primarily consists of single case studies that lack proper control conditions or involve only a single stimulation session. Due to their limited scope and power, these studies may not provide sufficient evidence. The current study expands upon existing research by investigating whether multiple sessions of repetitive transcranial magnetic stimulation over the SMA, combined with rhythmic speech, improve speech fluency in adults who stutter. Furthermore, it addresses the limitations of brain stimulation methods and proposes directions for future research. What are the potential or actual clinical implications of this work? This study implies that the stimulation of SMA reduced stuttering only in speaking contexts that may require greater motor control and coordination such as tongue twisters. Additionally, the research suggests that using rhythmic speech could potentially alleviate negative beliefs and anxiety associated with stuttering. **Research Findings:** * **Speech Fluency and Stuttering Severity:** The effects of excitatory rTMS on speech fluency were similar to the sham condition during oral reading and speaking tasks. However, a significant reduction in stuttering was observed in the production of tongue twisters post-rTMS (Mean %SS = 0.65%, SD = 0.44) compared to baseline (Mean %SS = 1.18%, SD = 0.91). This reduction was not seen in the sham condition. * **UTBAS-6 Scores:** Reductions in UTBAS-6 scores, which measure unhelpful thoughts and beliefs about stuttering, were noted in both active and sham conditions, but the reductions were numerically greater in the rTMS condition (approximately 10 points) than in the sham condition (approximately 5 points), although this difference was not statistically significant. This might be due to the sample size or the specific targeting of SMA, which primarily affects speech motor functions rather than psychological aspects. **Context and Comparisons:** * Previous studies have shown that anodal transcranial direct current stimulation (tDCS) to areas like the left inferior frontal gyrus (Broca’s area) improves speech fluency and reaction times in typically fluent individuals during tongue twister tasks. Some studies reported improvements, while others, such as Wong et al. (2019), did not find significant effects. * This study adds new evidence by focusing on adults who stutter (AWS) and showing that SMA stimulation can reduce stuttering in tongue twister tasks, suggesting that these tasks require greater motor control and coordination. **Challenges and Considerations:** * **Targeting SMA:** The SMA's deep anatomical location poses challenges for effective stimulation, which might explain the lack of significant results in reading and speaking tasks. The participants in this study had relatively mild stuttering, which could have obscured potential effects. * **Future Research:** Future studies should include participants with a broader range of stuttering severities and investigate various speech tasks. Exploring different stimulation montages and protocols, including inhibitory stimulation, might provide more insights. Moreover, targeting brain regions associated with emotion regulation could offer a better understanding of the effects on psychological aspects of stuttering. **Implications:** * Enhancing speech fluency through rhythmic speech training and rTMS may positively influence the psychological and cognitive aspects of stuttering. The reductions in UTBAS-6 scores, although not statistically significant, suggest that further research with larger sample sizes and alternative targeting could yield more definitive results. * Cognitive-behavioral therapy (CBT) remains a potent method for addressing the psychological aspects of stuttering, and future neuromodulation studies might benefit from integrating CBT principles. **Conclusion:** The findings of this study indicate that stimulating the SMA reduced stuttering, only in the production of tongue twisters that may require greater motor control and coordination. Furthermore, it indicates that rhythmic speech might help alleviate negative beliefs and anxiety related to stuttering. This research contributes to our understanding of neuromodulation in stuttering treatment and the role of the SMA in speech motor control and emphasises the need for more research on the potential benefits and limitations of applying rTMS in this condition. In conclusion, this study investigated the impact of combining excitatory rTMS of the SMA with rhythmic speech training in AWS. While treatment-induced improvements on stuttering severity and negative thoughts and beliefs about stuttering were observed, the effects were comparable between sham and rTMS conditions. Nevertheless, the rTMS condition led to reduced stuttering during the production of tongue twisters, while the sham condition did not yield the same effect. Further research is needed to better understand the potential benefits and limitations of neuromodulation methods especially TMS in stuttering treatments and to optimise the combined intervention approach. Results demonstrated improved speech fluency in var-ious speaking contexts, with no significant difference between rTMS and shamconditions immediately and  week post-treatment. Notably, rTMS specificallyled to less stuttering in tongue twister production (d=–.). Both treatmentconditions effectively reduced self-perceived stuttering severity and negativethoughts and beliefs about stuttering **Clinical implications:** This study implies that the stimulation of SMA reduced stuttering only in speaking contexts that may require greater motor control and coordination such as tongue twisters. Additionally, the research suggests that using rhythmic speech could potentially alleviate negative beliefs and anxiety associated with stuttering.