Brain activity during the preparation and production of spontaneous speech in children with persistent stuttering

Stuttering: Our Current Knowledge, Research Opportunities, and Ways to Address Critical Gaps

Our understanding of the neurobiological bases of stuttering remains limited, hampering development of effective treatments that are informed by basic science. Stuttering affects more than 5% of all preschool-age children and remains chronic in approximately 1% of adults worldwide. As a condition that affects a most fundamental human ability to engage in fluid and spontaneous verbal communication, stuttering can have substantial psychosocial, occupational, and educational impacts on those who are affected. This article summarizes invited talks and breakout sessions that were held in June 2023 as part of a 2-day workshop sponsored by the US National Institute on Deafness and Other Communication Disorders. The workshop encompassed topics including neurobiology, genetics, speech motor control, cognitive, social, and emotional impacts, and intervention. Updates on current research in these areas were summarized by each speaker, and critical gaps and priorities for future research were raised, and then discussed by participants. Research talks were followed by smaller, moderated breakout sessions intended to elicit diverse perspectives, including on the matter of defining therapeutic targets for stuttering. A major concern that emerged following participant discussion was whether priorities for treatment in older children and adults should focus on targeting core speech symptoms of stuttering, or on embracing effective communication regardless of whether the speaker exhibits overt stuttering. This article concludes with accumulated convergent points endorsed by most attendees on research and clinical priorities that may lead to breakthroughs with substantial potential to contribute to bettering the lives of those living with this complex speech disorder.

Mapping subcortical brain lesions, behavioral and acoustic analysis for early assessment of subacute stroke patients with dysarthria

Introduction

Dysarthria is a motor speech disorder frequently associated with subcortical damage. However, the precise roles of the subcortical nuclei, particularly the basal ganglia and thalamus, in the speech production process remain poorly understood.

Methods

The present study aimed to better understand their roles by mapping neuroimaging, behavioral, and speech data obtained from subacute stroke patients with subcortical lesions. Multivariate lesion-symptom mapping and voxel-based morphometry methods were employed to correlate lesions in the basal ganglia and thalamus with speech production, with emphases on linguistic processing and articulation.

Results

The present findings revealed that the left thalamus and putamen are significantly correlated with concept preparation (r = 0.64, p < 0.01) and word retrieval (r = 0.56, p < 0.01). As the difficulty of the behavioral tasks increased, the influence of cognitive factors on early linguistic processing gradually intensified. The globus pallidus and caudate nucleus were found to significantly impact the movements of the larynx (r = 0.63, p < 0.01) and tongue (r = 0.59, p = 0.01). These insights underscore the complex and interconnected roles of the basal ganglia and thalamus in the intricate processes of speech production. The lateralization and hierarchical organization of each nucleus are crucial to their contributions to these speech functions.

Discussion

The present study provides a nuanced understanding of how lesions in the basal ganglia and thalamus impact various stages of speech production, thereby enhancing our understanding of the subcortical neuromechanisms underlying dysarthria. The findings could also contribute to the identification of multimodal assessment indicators, which could aid in the precise evaluation and personalized treatment of speech impairments.

Influences of speaking task demands on sensorimotor oscillations in adults who stutter: Implications for speech motor control

OBJECTIVE

Motivated by previous inconsistent findings, this study aims to improve understanding of sensorimotor beta (β; 15-30 Hz) and alpha (α; 8-14 Hz) speech-related power differences between stuttering and non-stuttering adults.

METHODS

Electroencephalography was recorded as adults who stutter (AWS) and matched fluent controls answered questions in Quiet and Informational Masked backgrounds. Bilateral sensorimotor β and α power during speech planning and execution were measured from mu (μ) rhythm components.

RESULTS

Compared to controls, AWS exhibited reduced left hemisphere β and α power in both speaking conditions during speech planning and execution. AWS displayed reduced left α power in the Informational Masking compared to Quiet. Within AWS β and α power, which were tightly coupled, oppositely predicted stuttering severity and β-α dissociation (β minus α) was the strongest predictor.

CONCLUSION

Neither β nor α power are reliable markers of speech motor stability due to their sensitivity to speech task automaticity. However, relationships between these two sensorimotor rhythms warrant further investigation for understanding motor control.

SIGNIFICANCE

Data help explain previous mixed findings in reference to extant models of speech motor control in stuttering and may have clinical implications for developing neurostimulation protocols targeting improved speech fluency.

Erasmus clinical model of the onset and development of stuttering 2.0

A clinical, evidence-based model to inform clients and their parents about the nature of stuttering is indispensable for the field. In this paper, we propose the Erasmus Clinical Model of Stuttering 2.0 for children who stutter and their parents, and adult clients. It provides an up-to-date, clinical model summary of current insights into the genetic, neurological, motoric, linguistic, sensory, temperamental, psychological and social factors (be it causal, eliciting, or maintaining) related to stuttering. First a review is presented of current insights in these factors, and of six scientific theories or models that have inspired the development of our current clinical model. Following this, we will propose the model, which has proven to be useful in clinical practice. The proposed Erasmus Clinical Model of Stuttering visualizes the onset and course of stuttering, and includes scales for stuttering severity and impact, to be completed by the (parent of) the person who stutters. The pathway of the model towards stuttering onset is based on predisposing and mediating factors. In most children with an onset of stuttering, stuttering is transient, but if stuttering continues, its severity and impact vary widely. The model includes the circle of Engel (1977), which visualizes unique interactions of relevant biological, psychological, and social factors that determine the speaker's experience of stuttering severity and its impact. Discussing these factors and their interaction with an individual client can feed into therapeutic targets. The model is supplemented by a lifeline casus.

Knowns and unknowns about the neurobiology of stuttering

Stuttering occurs in early childhood during a dynamic phase of brain and behavioral development. The latest studies examining children at ages close to this critical developmental period have identified early brain alterations that are most likely linked to stuttering, while spontaneous recovery appears related to increased inter-area connectivity. By contrast, therapy-driven improvement in adults is associated with a functional reorganization within and beyond the speech network. The etiology of stuttering, however, remains enigmatic. This Unsolved Mystery highlights critical questions and points to neuroimaging findings that could inspire future research to uncover how genetics, interacting neural hierarchies, social context, and reward circuitry contribute to the many facets of stuttering.