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

June 28-29, 2023
Virtual Workshop

Workshop Summary

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NIDCD sponsored a virtual workshop on June 28-29, 2023: “Stuttering: Our Current Knowledge, Research Opportunities, and Ways to Address Critical Gaps.” The workshop reflected NIDCD’s long-standing efforts to encourage and support research on stuttering. The first NIDCD-sponsored workshop on stuttering was held in September 1988 and resulted in American Speech-Language-Hearing Association (ASHA) Report Number 18, Research Needs in Stuttering: Roadblocks and Future Directions (PDF | 6.2 MB). NIDCD subsequently sponsored a workshop titled State of the Science Conference: Developmental Stuttering on March 21-23, 2005.

The goal of the 2023 workshop was to gather a group of NIDCD-supported principal investigators, early career researchers, clinicians, and potential future grant applicants to discuss a variety of topics being addressed by funded investigators. A secondary goal was to foster future scientific collaboration among the group and encourage the preparation of new grant applications in the area of stuttering.

The speakers and discussants represented a wide range of backgrounds and perspectives. The organizers aimed to be maximally inclusive—especially of individuals who aren’t currently funded by the National Institutes of Health—and to structure the workshop to allow ample engagement and discussion in a virtual format. Organizers were mindful to include individuals who stutter and who could comment on the lived experience of stuttering. Professional liaisons to organizations focused on the needs of people who stutter were also invited to attend.

June 28 sessions

As noted in the agenda, the workshop covered five themes, with four of the themes covered on the first day. Debara L. Tucci, M.D., M.S., M.B.A., NIDCD Director, opened the workshop with a welcome, followed by Lana Shekim, Ph.D., Director of the NIDCD Voice and Speech Programs, who provided the workshop charge and an overview of the planned activities. NIDCD is grateful to Shelley Brundage, Ph.D., who served as timekeeper.

The first group of presentations reviewed the biological bases of stuttering. Jennifer Below, Ph.D., presented what we know about the genetics of stuttering and began her talk by highlighting the various approaches of study. She discussed studies using GWAS (genome-wide association studies) that show the polygenicity of stuttering consistent with a complex disease. She noted the need for larger sample sizes to elucidate genetic risk factors of this common yet complex trait.

Shahriar SheikhBahaei, Ph.D., then presented, noting that significant progress has been made toward identifying genetic risk factors in the pathophysiology of stuttering, but it is still unclear how mutations in the discovered genes may lead to stuttering. Animal models have proven invaluable in advancing our understanding of the neurogenetic mechanisms underlying brain function. Dr. SheikhBahaei uses a transgenic mouse model for stuttering. Using a combination of advanced imaging techniques, behavioral analysis, electrophysiology, and circuit mapping strategies, he presented the latest data from his group at the National Institute of Neurological Disorders and Stroke (NINDS), NIH, which suggest that glial cells may play a key role in the pathophysiology of stuttering.

Ho Ming Chow, Ph.D., presented on functional neuroimaging in people who stutter. He reported on a number of studies using fMRI while speakers were engaged in connected speech. He detailed his findings in various structures across populations and ages.

The last presentation in this section on the biological bases of stuttering was by Kate Watkins, Ph.D., who spoke on the effects of brain modulation on stuttering. She reported that transcranial direct current stimulation (tDCS) was found to be effective in reducing stuttering when combined with behavioral treatment, but not when provided alone.

The second set of presentations covered markers of persistence and recovery in stuttering. Bridget Walsh, Ph.D., began by highlighting behavioral indices of stuttering with the goal of discovering whether preschool children will persist in stuttering. She reviewed demographic factors associated with persistent stuttering, and she discussed work from her lab using physiological markers associated with persistent stuttering. Dr. Walsh then shared about current and future directions in her research using neurophysiologic measures (fNIRS and EEG) and autonomic and emotional measures during virtual reality scenarios, and the adverse impact of stuttering.

Soo-Eun Chang, Ph.D., followed by presenting on neurodevelopmental markers of stuttering persistence and noting the importance of studies using neuroimaging of the early childhood period to understand stuttering persistence. Dr. Chang reported on her longitudinal studies of more than 250 children and the differences between children who persisted with stuttering versus those who did not. She highlighted neural circuits of interest in stuttering, e.g., the fronto-temporal area, basal ganglia, and cerebellar regions.

The third set of presentations covered speech/motor control and stuttering. Ludo Max, Ph.D., began by addressing auditory-motor learning and stuttering. He posed several questions, including: What is different in people who stutter? Which differences are relevant? What are the underlying mechanisms?  The hypotheses can be tested by experiments informed by accepted theory (dating back to Neilson and Neilson, 1987). He discussed directionality (motor to sensory, and sensory to motor) and reviewed studies of the absence of these modulatory effects in people who stutter.

The second presentation in this session was by Frank Guenther, Ph.D., who spoke on computational models of stuttering. The models (his and others) focus on the core “deficit” in stuttering. He presented on his GODIVA model of speech sound sequencing with focus on feedforward control system and its two subcircuits: the initiation circuit and the articulation circuit. The take-home message was that “impaired” function in the cortico-BG loop for speech sequencing and initiation provides the most complete, current (as of June 2023) computational account of stuttering-like dysfluencies.

The fourth session focused on the cognitive and social factors of stuttering. Mandy Hampton Wray, Ph.D., spoke about executive function (EF), focusing on attention in developmental stuttering. Development of executive skills and language are interdependent. Inefficient or ineffective regulation of EF may influence efficiency of speech and language skills and could lead to disruptions in speech fluency. Attention plays a primary role in regulating goal-directed behavior. Parent reports indicate less focused attention in children who stutter compared to children who do not stutter. A recent study postulates that dysregulated interplay between attention and executive control, somatomotor, and internal control networks in children who stutter may influence the development of efficient execution of speech motor plans.

Eric Jackson, Ph.D., then presented on the social and cognitive features of stuttering events. Variability (intermittency) is a hallmark of stuttering. Dr. Jackson’s lab focuses on the single-word level. Social and cognitive features play a fundamental role in triggering or shaping stuttering events. The perception of a listener was seen as necessary for stuttering to occur. Dr. Jackson also shared results from his NIDCD early career research (ECR) R21 grant on neural responses prior to the stuttering event. He concluded that our science, particularly on the neurobiology of stuttering, needs to reflect what the speaker actually experiences. He also noted that a neurocognitive understanding of stuttering events could enhance treatment—both behaviorally, by increasing awareness of what happens when we stutter, and via targeted neuromodulation (e.g., tDCS).

June 29 sessions

On the second day of the workshop, the fifth session tackled various topics within the theme of treatment. The first presentation was by Nicole Neef, Ph.D., who spoke on brain changes associated with stuttering therapy. She emphasized how mapping the neural correlates of causes and consequences of stuttering fosters improved neurobiological understanding of stuttering. This in turn would determine the conditions and potentials of involved brain structures for neural reorganizations and support rational decisions for brain stimulation and pharmaceutical therapies. She reviewed stuttering studies under the magnifying lens of neuroimaging since 2001. These observations served as support of convergence from existing findings.

The next presentation, by Seth Tichenor, Ph.D., explored the impacts of stuttering and their relevance to therapy goals and approaches. He began by defining an adverse event as one with negative reactions (thoughts, feelings, or behaviors) and the broader speech- or communication-related limitations that a person who stutters experiences in daily life. He addressed severity of surface stuttering and called for a broad view of severity that accounts for subgroups of stutterers’ experiences. He also called for both a population-based and an individual perspective of stuttering. He presented preliminary data from his ongoing research and advocated for a more holistic view of a person’s experience of stuttering. He further stated that treatment solely focused on fluency may lead to more adverse impacts.

Scott Yaruss, Ph.D., spoke on defining aims for stuttering intervention. He asserted that stuttered speech shouldn’t be considered disordered just because it’s different. Some people who stutter experience it as a disorder, but not all do. He shared his comprehensive view of stuttering, adapted from the WHO International Classification of Functioning, Disability and Health (ICF) model. He cited NIH, NIDCD, and ASHA goals of improving people’s quality of life. Toward this goal, he encouraged a comprehensive view of stuttering intervention that links to the broader life experiences of people who stutter. He urged the rejection of ableist language and attitudes in order to build bridges with people who stutter.

The last presentation was by Nan Bernstein Ratner, Ph.D., on issues related to treating stuttering in young children. Dr. Bernstein Ratner began by asking whether any treatments work for young children who stutter. She reported that major studies show outcomes indistinguishable from spontaneous recovery (measurements were of surface stuttering behavior). Also, few studies have looked at adverse treatment impacts on children who stutter. Large scale studies across various languages and cultures have reported natural recovery rates in surface stuttering exceeding 70%. Dr. Bernstein Ratner then discussed examples of treatment, namely the Lidcombe method and indirect treatments (the Demands and Capacities Model, or DCM). Her current research shows that the components of DCM are mostly ineffective, and current therapies are equally ineffective. She cautioned that ineffective treatments may not be harmless—that they take from other options and potentially elevate parental feelings of guilt. She ended her presentation by calling for innovative treatments that cohere with the emerging science, a translational imagination, and commitment. She stressed both the importance of stratification of children by emerging predictors of remission/persistence and mindfulness toward inclusion of children from diverse backgrounds.

The workshop included time for questions/answers and discussion. After the five sessions were completed, Dr. Shekim shared a historical review of the NIDCD stuttering portfolio since 2001, with the group noting that more grants are currently funded than a decade ago.

Participants who wished were then divided into five breakout sessions that tackled the same three questions in each breakout. Leaders for the breakouts were pre-assigned and shared the results of the discussions with the larger group. The workshop adjourned at 5 p.m.

The workshop speakers are planning an article summarizing the content of the workshop for submission to a scientific journal.

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