Reorganization of brain function after a short-term behavioral intervention for stuttering

Functional and structural abnormalities of the speech disorders: a multimodal activation likelihood estimation meta-analysis

Speech disorders are associated with different degrees of functional and structural abnormalities. However, the abnormalities associated with specific disorders, and the common abnormalities shown by all disorders, remain unclear. Herein, a meta-analysis was conducted to integrate the results of 70 studies that compared 1843 speech disorder patients (dysarthria, dysphonia, stuttering, and aphasia) to 1950 healthy controls in terms of brain activity, functional connectivity, gray matter, and white matter fractional anisotropy. The analysis revealed that compared to controls, the dysarthria group showed higher activity in the left superior temporal gyrus and lower activity in the left postcentral gyrus. The dysphonia group had higher activity in the right precentral and postcentral gyrus. The stuttering group had higher activity in the right inferior frontal gyrus and lower activity in the left inferior frontal gyrus. The aphasia group showed lower activity in the bilateral anterior cingulate gyrus and left superior frontal gyrus. Across the four disorders, there were concurrent lower activity, gray matter, and fractional anisotropy in motor and auditory cortices, and stronger connectivity between the default mode network and frontoparietal network. These findings enhance our understanding of the neural basis of speech disorders, potentially aiding clinical diagnosis and intervention.

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.

Stuttering interventions for children, adolescents, and adults: a systematic review as a part of clinical guidelines

INTRODUCTION

Stuttering may have a holistic effect on the quality of life of a person who stutters by limiting participation in social situations, resulting in feelings of isolation and frustration, leading to difficulties in education and employment and increasing the likelihood of mental health problems. Even young children who stutter may have negative experiences of speaking. Therefore, it is important to treat stuttering behavior effectively in both children and adults. The purpose of this paper was to systematically review group and case studies about the effectiveness of behavioral stuttering interventions to provide evidence-based guidelines for clinicians.

METHODS

Systematic data retrieval was conducted in four electronic databases (PsycINFO, CINAHL, PubMed, Cochrane). The assessment of search results was conducted according to predetermined inclusion and exclusion criteria by two independent judges. The methodological quality of each paper was assessed using strict criteria to include only high-quality research.

RESULTS

The search revealed 2293 results, and 38 papers (systematic reviews N=3, group design studies N=21 and case studies N=14) with acceptable methodological quality were included. The data show that there is most evidence about the treatment of early childhood stuttering, very little evidence about school-aged children and some evidence about adults. The most convincing evidence is about the Lidcombe Program in the treatment of young children who stutter, but also other methods have promising evidence. Our data imply that in the treatment of adults who stutter, holistic treatments may influence speech fluency and overall experience of stuttering behavior. Speech restructuring treatments may have a positive effect on overt characteristics of stuttering, but not on covert stuttering behavior.

CONCLUSIONS

The results of this review agree with earlier reviews about the treatment of young children. However, due to different inclusion criteria, this review also shows the benefits of holistic treatment approaches with adults and adolescents.

Reinvestigating the Neural Bases Involved in Speech Production of Stutterers: An ALE Meta-Analysis

Background: Stuttering is characterized by dysfluency and difficulty in speech production. Previous research has found abnormalities in the neural function of various brain areas during speech production tasks. However, the cognitive neural mechanism of stuttering has still not been fully determined. Method: Activation likelihood estimation analysis was performed to provide neural imaging evidence on neural bases by reanalyzing published studies. Results: Our analysis revealed overactivation in the bilateral posterior superior temporal gyrus, inferior frontal gyrus, medial frontal gyrus, precentral gyrus, postcentral gyrus, basal ganglia, and cerebellum, and deactivation in the anterior superior temporal gyrus and middle temporal gyrus among the stutterers. The overactivated regions might indicate a greater demand in feedforward planning in speech production, while the deactivated regions might indicate dysfunction in the auditory feedback system among stutterers. Conclusions: Our findings provide updated and direct evidence on the multi-level impairment (feedforward and feedback systems) of stutterers during speech production and show that the corresponding neural bases were differentiated.

Multimodal explainable AI predicts upcoming speech behavior in adults who stutter

A key goal of cognitive neuroscience is to better understand how dynamic brain activity relates to behavior. Such dynamics, in terms of spatial and temporal patterns of brain activity, are directly measured with neurophysiological methods such as EEG, but can also be indirectly expressed by the body. Autonomic nervous system activity is the best-known example, but, muscles in the eyes and face can also index brain activity. Mostly parallel lines of artificial intelligence research show that EEG and facial muscles both encode information about emotion, pain, attention, and social interactions, among other topics. In this study, we examined adults who stutter (AWS) to understand the relations between dynamic brain and facial muscle activity and predictions about future behavior (fluent or stuttered speech). AWS can provide insight into brain-behavior dynamics because they naturally fluctuate between episodes of fluent and stuttered speech behavior. We focused on the period when speech preparation occurs, and used EEG and facial muscle activity measured from video to predict whether the upcoming speech would be fluent or stuttered. An explainable self-supervised multimodal architecture learned the temporal dynamics of both EEG and facial muscle movements during speech preparation in AWS, and predicted fluent or stuttered speech at 80.8% accuracy (chance=50%). Specific EEG and facial muscle signals distinguished fluent and stuttered trials, and systematically varied from early to late speech preparation time periods. The self-supervised architecture successfully identified multimodal activity that predicted upcoming behavior on a trial-by-trial basis. This approach could be applied to understanding the neural mechanisms driving variable behavior and symptoms in a wide range of neurological and psychiatric disorders. The combination of direct measures of neural activity and simple video data may be applied to developing technologies that estimate brain state from subtle bodily signals.

White matter tract strength correlates with therapy outcome in persistent developmental stuttering

Persistent stuttering is a prevalent neurodevelopmental speech disorder, which presents with involuntary speech blocks, sound and syllable repetitions, and sound prolongations. Affected individuals often struggle with negative feelings, elevated anxiety, and low self-esteem. Neuroimaging studies frequently link persistent stuttering with cortical alterations and dysfunctional cortico-basal ganglia-thalamocortical loops; dMRI data also point toward connectivity changes of the superior longitudinal fasciculus (SLF) and the frontal aslant tract (FAT). Both tracts are involved in speech and language functions, and the FAT also supports inhibitory control and conflict monitoring. Whether the two tracts are involved in therapy-associated improvements and how they relate to therapeutic outcomes is currently unknown. Here, we analyzed dMRI data of 22 patients who participated in a fluency-shaping program, 18 patients not participating in therapy, and 27 fluent control participants, measured 1 year apart. We used diffusion tractography to segment the SLF and FAT bilaterally and to quantify their microstructural properties before and after a fluency-shaping program. Participants learned to speak with soft articulation, pitch, and voicing during a 2-week on-site boot camp and computer-assisted biofeedback-based daily training for 1 year. Therapy had no impact on the microstructural properties of the two tracts. Yet, after therapy, stuttering severity correlated positively with left SLF fractional anisotropy, whereas relief from the social-emotional burden to stutter correlated negatively with right FAT fractional anisotropy. Thus, posttreatment, speech motor performance relates to the left dorsal stream, while the experience of the adverse impact of stuttering relates to the structure recently associated with conflict monitoring and action inhibition.

Structural brain network topological alterations in stuttering adults

Persistent developmental stuttering is a speech disorder that primarily affects normal speech fluency but encompasses a complex set of symptoms ranging from reduced sensorimotor integration to socioemotional challenges. Here, we investigated the whole brain structural connectome and its topological alterations in adults who stutter. Diffusion weighted imaging data of 33 subjects (13 adults who stutter and 20 fluent speakers) was obtained along with a stuttering severity evaluation. The structural brain network properties were analyzed using Network-based statistics and graph theoretical measures particularly focusing on community structure, network hubs and controllability. Bayesian power estimation was used to assess the reliability of the structural connectivity differences by examining the effect size. The analysis revealed reliable and wide-spread decreases in connectivity for adults who stutter in regions associated with sensorimotor, cognitive, emotional, and memory-related functions. The community detection algorithms revealed different subnetworks for fluent speakers and adults who stutter, indicating considerable network adaptation in adults who stutter. Average and modal controllability differed between groups in a subnetwork encompassing frontal brain regions and parts of the basal ganglia.

The results revealed extensive structural network alterations and substantial adaptation in neural architecture in adults who stutter well beyond the sensorimotor network. These findings highlight the impact of the neurodevelopmental effects of persistent stuttering on neural organization and the importance of examining the full structural connectome and the network alterations that underscore the behavioral phenotype.

Fluency shaping increases integration of the command-to-execution and the auditory-to-motor pathways in persistent developmental stuttering

Fluency-shaping enhances the speech fluency of persons who stutter, yet underlying conditions and neuroplasticity-related mechanisms are largely unknown. While speech production-related brain activity in stuttering is well studied, it is unclear whether therapy repairs networks of altered sensorimotor integration, imprecise neural timing and sequencing, faulty error monitoring, or insufficient speech planning. Here, we tested the impact of one-year fluency-shaping therapy on resting-state fMRI connectivity within sets of brain regions subserving these speech functions. We analyzed resting-state data of 22 patients who participated in a fluency-shaping program, 18 patients not participating in therapy, and 28 fluent control participants, measured one year apart. Improved fluency was accompanied by an increased connectivity within the sensorimotor integration network. Specifically, two connections were strengthened; the left inferior frontal gyrus showed increased connectivity with the precentral gyrus at the representation of the left laryngeal motor cortex, and the left inferior frontal gyrus showed increased connectivity with the right superior temporal gyrus. Thus, therapy-associated neural remediation was based on a strengthened integration of the command-to-execution pathway together with an increased auditory-to-motor coupling. Since we investigated task-free brain activity, we assume that our findings are not biased to network activity involved in compensation but represent long-term focal neuroplasticity effects.

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

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.

Bilinguals who stutter: A cognitive perspective

PURPOSE

Brain differences, both in structure and executive functioning, have been found in both developmental stuttering and bilingualism. However, the etiology of stuttering remains unknown. The early suggestion that stuttering is a result of brain dysfunction has since received support from various behavioral and neuroimaging studies that have revealed functional and structural brain changes in monolinguals who stutter (MWS). In addition, MWS appear to show deficits in executive control. However, there is a lack of data on bilinguals who stutter (BWS). This literature review is intended to provide an overview of both stuttering and bilingualism as well as synthesize areas of overlap among both lines of research and highlight knowledge gaps in the current literature.

METHODS

A systematic literature review on both stuttering and bilingualism studies was conducted, searching for articles containing "stuttering" and/or "bilingualism" and either "brain", "executive functions", "executive control", "motor control", "cognitive reserve", or "brain reserve" in the PubMed database. Additional studies were found by examining the reference list of studies that met the inclusion criteria.

RESULTS

A total of 148 references that met the criteria for inclusion in this paper were used in the review. A comparison of the impact of stuttering or bilingualism on the brain are discussed.

CONCLUSION

Previous research examining a potential bilingual advantage for BWS is mixed. However, if such an advantage does exist, it appears to offset potential deficits in executive functioning that may be associated with stuttering.

Effectiveness of nonpharmacological stuttering interventions on communication and psychosocial functioning in adults: A systematic review and meta-analysis of randomized controlled trials

OBJECTIVE

To conduct a systematic review and meta-analysis of the research evidence examining the effectiveness of nonpharmacological stuttering therapy on communication and psychosocial functioning for adults who stutter.

METHODS

A systematic search of nine electronic databases for studies published from database inception to December 2018 was completed to identify randomized controlled trials of interventions for adults with developmental stuttering. Two reviewers independently screened articles and assessed methodological quality using the Cochrane risk-of-bias tool. Treatment outcomes were classified using the International Classification of Functioning, Disability and Health (ICF) framework.

RESULTS

The search yielded nine randomized controlled trials, comprising 276 participants, using a diverse range of interventions which were classified into four categories: speech restructuring interventions; speech restructuring plus psychological interventions; interventions with stimulating techniques and interventions targeting anxiety. Meta-analysis showed that interventions did not demonstrate a significant pooled difference when compared to comparison groups in improving speech fluency (standardized mean difference [SMD] = -0.35, 95% confidence interval [CI] -1.14 to 0.45, I²   = 81%, P = .39), overall experience of stuttering (mean difference [MD] = -0.10, 95% CI -0.36 to 0.15, I²   = 0%, P = .43) and quality of life (SMD = -0.32, 95% CI -0.83 to 0.19, I²   = 0%, P = .21).

CONCLUSIONS

This article identified a diverse range of treatments and outcome measures for adults who stutter, with meta-analysis highlighting no significant pooled difference between intervention and comparator groups in improving communication and psychosocial functioning.

Long-latency auditory evoked potential in children with stuttering

Objective

To analyze the latency and the amplitude values of Mismatch Negativity and P300 cognitive potential in children with stuttering, with no auditory complaints, with auditory thresholds within the normality range, comparing them to the findings of a Control Group.

Methods

A cross-sectional study involving 50 children of both sexes, 15 with stuttering and 35 without stuttering, aged 6 to 11 years, with no diagnosis of ear pathology or other diseases. All children were submitted to peripheral audiological evaluation (meatoscopy, pure tone testing, speech audiometry, and acoustic immittance measures) and a central audiological evaluation (investigation of the Mismatch Negativity and P300 cognitive potential). For the evaluation of fluency, all children with stuttering had a specific history taken and were video recorded in a spontaneous speech. Afterwards, the transcription was done, followed by speech analysis to classify children according the severity of stuttering.

Results

There was a significant difference in the latencies of Mismatch Negativity and P300 cognitive potential, as well as in the amplitude of Mismatch Negativity.

Conclusion

There was a significant delay in the latencies of Mismatch Negativity and P300 cognitive potential, as well as increase in the amplitude of the Mismatch Negativity in children with stuttering when compared to children in the Control Group. Changes in the morphology of the waves were found in the Stuttering Group.

Implication of N400 and P600 waves in the Linguistic Code Change in Monolinguals and Bilinguals

There is evidence of the importance of N400 and P600 waves in linguistic processes, theses brain waves are related to syntax. This work proposes to evaluate learning process through the analysis of responses generated when formulation of word is requested, an artificial grammar test (AGT) is developed and N400 and P600 peaks are taken as indicators of performance; and two different groups of subjects took the AGT, 5 monolinguals and 5 bilinguals.The AGT is composed by 30 hybrids, each hybrid defines rules to formulate words; then if this word accomplished the rules, it is considered as grammatical. The N400 and P600 waves are computed by each word letter, and the mean for all 30 hybrids is compared between both two groups by electrode.Greater amplitudes for N400 and P600 peaks was found for monolinguals in comparison with bilinguals.