Speech Fluency Improvement in Developmental Stuttering Using Non-invasive Brain Stimulation: Insights From Available Evidence

Abstract

Developmental stuttering (DS) is a disturbance of the normal rhythm of speech that may be interpreted as very debilitating in the most affected cases. Interventions for DS are historically based on the behavioral modifications of speech patterns (e.g., through speech therapy), which are useful to regain a better speech fluency. However, a great variability in intervention outcomes is normally observed, and no definitive evidence is currently available to resolve stuttering, especially in the case of its persistence in adulthood. In the last few decades, DS has been increasingly considered as a functional disturbance, affecting the correct programming of complex motor sequences such as speech. Compatibly, understanding of the neurophysiological bases of DS has dramatically improved, thanks to neuroimaging, and techniques able to interact with neural tissue functioning [e.g., non-invasive brain stimulation (NIBS)]. In this context, the dysfunctional activity of the cortico-basal-thalamo-cortical networks, as well as the defective patterns of connectivity, seems to play a key role, especially in sensorimotor networks. As a consequence, a direct action on the functionality of “defective” or “impaired” brain circuits may help people who stutter to manage dysfluencies in a better way. This may also “potentiate” available interventions, thus favoring more stable outcomes of speech fluency. Attempts aiming at modulating (and improving) brain functioning of people who stutter, realized by using NIBS, are quickly increasing. Here, we will review these recent advancements being applied to the treatment of DS. Insights will be useful not only to assess whether the speech fluency of people who stutter may be ameliorated by acting directly on brain functioning but also will provide further suggestions about the complex and dynamic pathophysiology of DS, where causal effects and “adaptive''/‘‘maladaptive” compensation mechanisms may be strongly overlapped. In conclusion, this review focuses future research toward more specific, targeted, and effective interventions for DS, based on neuromodulation of brain functioning.

Abstracts of the 8th International Conference on Speech Motor Control Groningen, August 2022

“…For these reasons, we bring together articulatory phonetics and machine learning to investigate new ways of describing the trajectories of supraglottic speech articulators during Stuttering-Like Disfluencies (SLD) produced by Persons Who Stutter (PWS) and Other Disfluencies (OD) produced both by PWS and Persons Who do Not Stutter (PWNS). Due to spasmodic movements (Busan et al, 2021), we hypothesize that supraglottic articulatory trajectories should exhibit more deviation from their primary trajectory (i.e., the expected up-/downward or forward/backward movement) compared to OD. To test our hypothesis, we approximate the primary trajectory by computing a cubic regression for each configuration (i.e., a couple (axis, articulator)) and each disfluency.…”

“…These results demonstrate that it is possible to distinguish SLD from OD even with limited data. Based on these results, we are now experimenting the use of machine learning algorithms, such as autoencoders (Tschannen et al, 2018), to estimate what we can learn from these models using limited data. The contribution of our observations to speech production in PWS and automatic detection of stuttering events will be discussed during the conference.…”

Psychedelics in developmental stuttering to modulate brain functioning: a new therapeutic perspective?

“…Speech therapy is the most commonly used treatment, but relapse is common ( Qureshi et al, 2021 ). Neuromodulation and pharmacology are also increasingly investigated (for recent reviews see Maguire et al, 2020 ; Busan et al, 2021 ; Qureshi et al, 2021 ; see also Chesters et al, 2018 , Garnett et al, 2019 ; Busan et al, 2023 ). For example, experimental pharmacological interventions in DS modulate the (nigro-striatal) dopaminergic system of the brain, typically by means of dopamine antagonists (e.g., at D2 [risperidone or olanzapine] and D1 receptors [ecopipam]; Maguire et al, 2020 ).…”

The Contribution of the Supplementary Motor Area to Explicit and Implicit Timing: A High-Definition Transcranial Random Noise Stimulation (HD-tRNS) Study

“…This result aligns well with further fMRI data showing increased SMA activity during foreperiod tasks ( [26,27]; see also [28]). There is also evidence that the SMA is a fundamental "hub" of a cortico-basal-thalamo-cortical network involved in the internal (implicit) timing of voluntary planning/execution in complex sequences, such as speech (see [29,30]).…”

“…In addition to TMS, transcranial electric stimulation (tES) techniques, including transcranial Direct Current Stimulation (tDCS), transcranial Alternating Current Stimulation (tACS), and transcranial Random Noise Stimulation (tRNS), are rapidly growing in the investigation of the neural correlates of time perception (see [37], for a review) and sensorimotor processes (see [30]). Although the majority of tES studies on explicit timing tasks (e.g., temporal discrimination, temporal reproduction, and temporal bisection tasks) have mainly used tDCS [40][41][42][43], it should be noted that the commonly assumed cathodal/inhibition and anodal/facilitation tDCS effects on the motor system are not so clear in the cognitive domain [44][45][46].…”