Speech-induced suppression of evoked auditory fields in children who stutter

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.

Examining resting state functional connectivity and frequency power analysis in adults who stutter compared to adults who do not stutter

Introduction

Stuttering is a speech disorder characterized by impaired connections between brain regions involved in speech production. This study aimed to investigate functional connectivity and frequency power during rest in adults who stutter (AWS) compared to fluent adults (AWNS) in the dorsolateral prefrontal cortex (DLPFC), dorsolateral frontal cortex (DLFC), supplementary motor area (SMA), motor speech, angular gyrus (AG), and inferior temporal gyrus (ITG).

Materials and methods

Fifteen AWS (3 females, 12 males) and fifteen age- and sex-matched AWNS (3 females, 12 males) participated in this study. All participants were native Persian speakers. Stuttering severity in the AWS group was assessed using the Persian version of the Stuttering Severity Instrument Fourth Edition (SSI-4). Resting-state electroencephalography (EEG) was recorded for 5 min while participants sat comfortably with their eyes open. We analyzed frequency band power across various frequency bands and investigated functional connectivity within the specified speech region.

Results

Significant between-group differences were found in band powers including alpha, beta, delta, theta, and gamma, specifically in the premotor, SMA, motor speech, and frontal regions. AWS also showed increased coherence between the right motor speech region compared to controls. We demonstrate that the proposed hierarchical false discovery rate (FDR) method is the most effective for both simulations and experimental data. In the expected regions, this method revealed significant synchrony effects at an acceptable error rate of 5%.

Conclusion

The results highlight disrupted functional connectivity in AWS at resting state, particularly in speech-related and associated areas. Given the complex neurological basis of developmental stuttering, robust neural markers are closely linked to this phenomenon. These markers include imbalanced activity within brain regions associated with speech and motor functions, coupled with impaired functional connectivity between these regions. The cortico-basal ganglia-thalamo-cortical system governs the dynamic interplay between cortical regions, with SMA as a key cortical site. It is hypothesized that the aberrant resting state functional connectivity will impact the language planning and motor execution necessary for fluent speech. Examining resting-state metrics as biomarkers could further elucidate the neural underpinnings of stuttering and guide intervention.

The relation between long latency cortical auditory evoked potentials and stuttering severity in stuttering school-age children

BACKGROUND

Disturbances in auditory processing and feedback have been suggested to play a role in the pathogenesis of developmental stuttering. Long latency cortical auditory evoked potentials in response to non-linguistic and linguistic stimuli can be used to investigate these disturbances. There were differences between developmental stuttering patients. However, there is no solid evidence of these differences to date.

OBJECTIVE

This study aims to determine whether there is a statistically significant difference in component P1-N1-P2 of long latency cortical auditory evoked potentials between stuttering school-aged children and non-stuttering children. In addition, the study aims to investigate the relationship between these potentials and objective quantitative measures of stuttering.

METHOD

The study included two groups, patients and controls, consisting of 40 subjects aged 6-12 years. For the cases group, the severity of stuttering symptoms and P1-N1-P2 responses to a non-linguistic stimulus were evaluated. In addition, the P1-N1-P2 responses of the matched control group were evaluated.

RESULTS

The P1-N1 responses were similar in both study groups, while P2 response was shorter in the patient group, but the difference was not statistically significant compared to the control group. N1 latency has the only statistically significant correlation with the percentage of repetitions, prolongation, and blocks. The female cases had a decreased, not statistically significant, latency than the male cases group.

CONCLUSION

In contrast to the previous finding, the study revealed a non-statistically significant different P1-N1, a non-statistically significant reduced P2 response to a non-linguistic stimulus, in CWS, in as evidence for basic auditory processing. The study also revealed a significant correlation between N1 latency and proportion of the repetition symptoms.

Modeling Responses to Auditory Feedback Perturbations in Adults, Children, and Children With Complex Speech Sound Disorders: Evidence for Impaired Auditory Self-Monitoring?

PURPOSE

Previous studies have found that typically developing (TD) children were able to compensate and adapt to auditory feedback perturbations to a similar or larger degree compared to young adults, while children with speech sound disorder (SSD) were found to produce predominantly following responses. However, large individual differences lie underneath the group-level results. This study investigates possible mechanisms in responses to formant shifts by modeling parameters of feedback and feedforward control of speech production based on behavioral data.

METHOD

SimpleDIVA was used to model an existing dataset of compensation/adaptation behavior to auditory feedback perturbations collected from three groups of Dutch speakers: 50 young adults, twenty-three 4- to 8-year-old children with TD speech, and seven 4- to 8-year-old children with SSD. Between-groups and individual within-group differences in model outcome measures representing auditory and somatosensory feedback control gain and feedforward learning rate were assessed.

RESULTS

Notable between-groups and within-group variation was found for all outcome measures. Data modeled for individual speakers yielded model fits with varying reliability. Auditory feedback control gain was negative in children with SSD and positive in both other groups. Somatosensory feedback control gain was negative for both groups of children and marginally negative for adults. Feedforward learning rate measures were highest in the children with TD speech followed by children with SSD, compared to adults.

CONCLUSIONS

The SimpleDIVA model was able to account for responses to the perturbation of auditory feedback other than corrective, as negative auditory feedback control gains were associated with following responses to vowel shifts. These preliminary findings are suggestive of impaired auditory self-monitoring in children with complex SSD. Possible mechanisms underlying the nature of following responses are discussed.

Effect of an Auditory Temporal Training Program on Speech Fluency of Children with Developmental Stuttering

Objectives

The present study aims to investigate the effect of a temporal processing-based auditory training program on alleviating stuttering severity in children diagnosed with auditory temporal processing disorders.

Materials & Methods

Thirty-one children with stuttering diagnosed with auditory temporal processing disorders participated in this study (intervention group: 17 participants between seven to 12 years old; control group: 14 participants between eight to 12 years old). The auditory temporal processing test and Stuttering Severity Instrument-3 (SSI-3) were examined before/after 12 sessions (nearly 540 minutes) of training and three months following the conclusion of the intervention.

Results

According to the results, auditory temporal processing improved significantly in the intervention group after temporal processing-based auditory training. Besides, the differences between the intervention and control groups were significant (P<0.05). The improvement of auditory temporal processing skills remained stable in the post-training evaluation after three months (P>0.05). Although the SSI-3 score was somewhat improved in the intervention group, no significant difference was found between the two groups (P=0.984).

Conclusion

The findings revealed that auditory temporal processing training acted as a complementary therapy alleviating the stuttering severity of children who stutter with auditory temporal processing disorders to some extent.

Impaired Categorical Perception of Speech Sounds Under the Backward Masking Condition in Adults Who Stutter

PURPOSE

Evidence increasingly indicates that people with developmental stuttering have auditory perception deficits. Our previous research has indicated similar but slower performance in categorical perception of the speech sounds under the quiet condition in children who stutter and adults who stutter (AWS) compared with their typically fluent counterparts. We hypothesized that the quiet condition may not be sufficiently sensitive to reveal subtle perceptual deficiencies in people who stutter. This study examined this hypothesis by testing the categorical perception of speech and nonspeech sounds under backward masking condition (i.e., a noise was presented immediately after the target stimuli).

METHOD

Fifteen Cantonese-speaking AWS and 15 adults who do not stutter (AWNS) were tested on the categorical perception of four stimulus continua, namely, consonant varying in voice onset time (VOT), vowel, lexical tone, and nonspeech, under the backward masking condition using identification and discrimination tasks.

RESULTS

AWS demonstrated a broader boundary width than AWNS in the identification task. AWS also exhibited a worse performance than AWNS in the discrimination of between-category stimuli but a comparable performance in the discrimination of within-category stimuli, indicating reduced sensitivity to sounds that belonged to different phonemic categories among AWS. Moreover, AWS showed similar patterns of impaired categorical perception across the four stimulus types, although the boundary location on the VOT continuum occurred at an earlier point in AWS than in AWNS.

CONCLUSIONS

The findings provide robust evidence that AWS exhibit impaired categorical perception of speech and nonspeech sounds under the backward masking condition. Temporal processing (i.e., VOT manipulation), frequency/spectral/formant processing (i.e., lexical tone or vowel manipulations), and nonlinguistic pitch processing were all found to be impaired in AWS. Altogether, the findings support the hypothesis that AWS might be less efficient in accessing the phonemic representations when exposed to a demanding listening condition.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.20249718.

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.

Audiovisual incongruence differentially impacts left and right hemisphere sensorimotor oscillations: Potential applications to production

Speech production gives rise to distinct auditory and somatosensory feedback signals which are dynamically integrated to enable online monitoring and error correction, though it remains unclear how the sensorimotor system supports the integration of these multimodal signals. Capitalizing on the parity of sensorimotor processes supporting perception and production, the current study employed the McGurk paradigm to induce multimodal sensory congruence/incongruence. EEG data from a cohort of 39 typical speakers were decomposed with independent component analysis to identify bilateral mu rhythms; indices of sensorimotor activity. Subsequent time-frequency analyses revealed bilateral patterns of event related desynchronization (ERD) across alpha and beta frequency ranges over the time course of perceptual events. Right mu activity was characterized by reduced ERD during all cases of audiovisual incongruence, while left mu activity was attenuated and protracted in McGurk trials eliciting sensory fusion. Results were interpreted to suggest distinct hemispheric contributions, with right hemisphere mu activity supporting a coarse incongruence detection process and left hemisphere mu activity reflecting a more granular level of analysis including phonological identification and incongruence resolution. Findings are also considered in regard to incongruence detection and resolution processes during production.

Weak Vestibular Response in Persistent Developmental Stuttering

Vibrational energy created at the larynx during speech will deflect vestibular mechanoreceptors in humans (Todd et al., 2008; Curthoys, 2017; Curthoys et al., 2019). Vestibular-evoked myogenic potential (VEMP), an indirect measure of vestibular function, was assessed in 15 participants who stutter, with a non-stutter control group of 15 participants paired on age and sex. VEMP amplitude was 8.5 dB smaller in the stutter group than the non-stutter group (p = 0.035, 95% CI [−0.9, −16.1], t = −2.1, d = −0.8, conditional R² = 0.88). The finding is subclinical as regards gravitoinertial function, and is interpreted with regard to speech-motor function in stuttering. There is overlap between brain areas receiving vestibular innervation, and brain areas identified as important in studies of persistent developmental stuttering. These include the auditory brainstem, cerebellar vermis, and the temporo-parietal junction. The finding supports the disruptive rhythm hypothesis (Howell et al., 1983; Howell, 2004) in which sensory inputs additional to own speech audition are fluency-enhancing when they coordinate with ongoing speech.

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.

Functional brain networks underlying automatic and controlled handwriting in Chinese

This study aimed to identify the functional brain networks underlying the distinctions between automatic and controlled handwriting in Chinese. Network-based analysis was applied to functional magnetic resonance imaging data collected while adult participants performed a copying task under automatic and speed-controlled conditions. We found significant differences between automatic and speed-controlled handwriting in functional connectivity within and between the frontoparietal network, default mode network, dorsal attention network, somatomotor network and visual network; these differences reflect the variations in general attentional control and task-relevant visuomotor operations. However, no differences in brain activation were detected between the two handwriting conditions, suggesting that the reorganization of functional networks, rather than the modulation of local brain activation, underlies the dissociations between automatic and controlled handwriting in Chinese. Our findings illustrate the brain basis of handwriting automaticity, shedding new light on how handwriting automaticity may be disrupted in individuals with neurological disorders.

Motor sequence learning in children with recovered and persistent developmental stuttering: preliminary findings

PURPOSE

Previous studies have associated developmental stuttering with difficulty learning new motor skills. We investigated non-speech motor sequence learning in children with persistent developmental stuttering (CWS), children who have recovered from developmental stuttering (CRS) and typically developing controls (CON).

METHODS

Over the course of two days, participants completed the Multi-Finger Sequencing Task, consisting of repeated trials of a10-element sequence, interspersed with trials of random sequences of the same length. We evaluated motor sequence learning using accuracy and response synchrony, a timing measure for evaluation of sequencing timing. We examined error types as well as recognition and recall of the repeated sequences.

RESULTS

CWS demonstrated lower performance accuracy than CON and CRS on the first day of the finger tapping experiment but improved to the performance level of CON and CRS on the second day. Response synchrony showed no overall difference among CWS, CRS and CON. Learning scores of repeated sequences did not differ from learning scores of random sequences in CWS, CRS and CON. CON and CRS demonstrated an adaptive strategy to response errors, whereas CWS maintained a high percentage of corrected errors for both days.

CONCLUSIONS

Our study examined non-speech sequence learning across CWS, CRS and CON. Our preliminary findings support the idea that developmental stuttering is not associated with sequence learning per se but rather with general fine motor performance difficulties.

Neural Indices Mediating Rhyme Discrimination Differ for Some Young Children Who Stutter Regardless of Eventual Recovery or Persistence

Purpose Previous studies of neural processing of rhyme discrimination in 7- to 8-year-old children who stutter (CWS) distinguished children who had recovered, children who had persisted, and children who did not stutter (CWNS; Mohan & Weber, 2015). Here, we investigate neural processing mediating rhyme discrimination for early acquired real words in younger CWS and CWNS (4;1-6;0 years;months), when rhyming abilities are newly emerging, to examine possible relationships to eventual recovery (CWS-eRec) and persistence in stuttering (CWS-ePer). Method Children performed a rhyme discrimination task while their event-related brain potentials were recorded. CWNS, CWS-eRec, and CWS-ePer had similar speech and language abilities. Inclusionary criteria incorporated at least 70% accuracy for rhyme discrimination. Analyses focused on the mean amplitude of the N400 component elicited by rhyming and nonrhyming words in anterior and posterior regions of interest. Results CWNS, CWS-eRec, and CWS-ePer displayed a classic event-related potential rhyme effect for rhyme discrimination characterized by larger amplitude, posteriorly distributed N400s elicited by nonrhyming targets compared to rhyming targets. CWNS displayed a more robust anterior rhyme effect compared to the CWS groups with a larger amplitude N400 anteriorly for the rhyming targets. This effect was more consistent across individual CWNS than CWS. Conclusions The groups of CWNS, CWS-eRec, and CWS-ePer, who had all developed rhyming discrimination abilities, exhibited similar underlying neural processes mediating phonological processing of early acquired words for the classic central-parietal rhyme effect. However, individual variability of the anterior rhyme effect suggested differences in specific aspects of phonological processing for some CWS-eRec and CWS-ePer compared to CWNS.

Speech-Induced Suppression for Delayed Auditory Feedback in Adults Who Do and Do Not Stutter

Speech-induced suppression is the normal, relative amplitude reduction of the auditory evoked potential for self-, compared to externally-generated, auditory stimulation. It remains controversial as to whether adults who stutter exhibit expected auditory modulation during speech; some studies have reported a significant difference between stuttering and fluent groups in speech-induced suppression during speech movement planning, while others have not. We compared auditory evoked potentials (N1 component) for auditory feedback arising from one’s own voice (Speaking condition) with passive listening to a recording of one’s own voice (Listening condition) in 24 normally-fluent speakers and 16 adults who stutter under various delayed auditory feedback (DAF) time conditions (100 ms, 200 ms, 500 ms, and 1,000 ms). We presented the participant’s own voice with a delay, immediately after presenting it without a delay. Our working hypothesis was that the shorter the delay time, the more likely the delayed sound is perceived as self-generated. Therefore, shorter delay time conditions are proposed to result in relatively enhanced suppression of the auditory system. Results showed that in fluent speakers, the shorter the delay time, the more the auditory evoked potential in the Speaking condition tended to be suppressed. In the Listening condition, there was a larger evoked potential with shorter delay times. As a result, speech-induced suppression was only significant at the short delay time conditions of 100 and 200 ms. Adults who stutter did not show the opposing changes in the Speaking and Listening conditions seen in the fluent group. Although the evoked potential in the Listening condition tended to decrease as the delay time increased, that in the Speaking condition did not show a distinct trend, and there was a significant suppression only at 200 ms delay. For the 200 ms delay condition, speakers with more severe stuttering showed significantly greater speech-induced suppression than those with less severe stuttering. This preliminary study suggests our methods for investigating evoked potentials by presenting own voice with a delay may provide a clue as to the nature of auditory modulation in stuttering.

Neural Correlates of Vocal Pitch Compensation in Individuals Who Stutter

Stuttering is a disorder that impacts the smooth flow of speech production and is associated with a deficit in sensorimotor integration. In a previous experiment, individuals who stutter were able to vocally compensate for pitch shifts in their auditory feedback, but they exhibited more variability in the timing of their corrective responses. In the current study, we focused on the neural correlates of the task using functional MRI. Participants produced a vowel sound in the scanner while hearing their own voice in real time through headphones. On some trials, the audio was shifted up or down in pitch, eliciting a corrective vocal response. Contrasting pitch-shifted vs. unshifted trials revealed bilateral superior temporal activation over all the participants. However, the groups differed in the activation of middle temporal gyrus and superior frontal gyrus [Brodmann area 10 (BA 10)], with individuals who stutter displaying deactivation while controls displayed activation. In addition to the standard univariate general linear modeling approach, we employed a data-driven technique (independent component analysis, or ICA) to separate task activity into functional networks. Among the networks most correlated with the experimental time course, there was a combined auditory-motor network in controls, but the two networks remained separable for individuals who stuttered. The decoupling of these networks may account for temporal variability in pitch compensation reported in our previous work, and supports the idea that neural network coherence is disturbed in the stuttering brain.

Theta Modulated Neural Phase Coherence Facilitates Speech Fluency in Adults Who Stutter

Adults who stutter (AWS) display altered patterns of neural phase coherence within the speech motor system preceding disfluencies. These altered patterns may distinguish fluent speech episodes from disfluent ones. Phase coherence is relevant to the study of stuttering because it reflects neural communication within brain networks. In this follow-up study, the oscillatory cortical dynamics preceding fluent speech in AWS and adults who do not stutter (AWNS) were examined during a single-word delayed reading task using electroencephalographic (EEG) techniques. Compared to AWNS, fluent speech preparation in AWS was characterized by a decrease in theta-gamma phase coherence and a corresponding increase in theta-beta coherence level. Higher spectral powers in the beta and gamma bands were also observed preceding fluent utterances by AWS. Overall, there was altered neural communication during speech planning in AWS that provides novel evidence for atypical allocation of feedforward control by AWS even before fluent utterances.

Abnormal processing of prosodic boundary in adults who stutter: An ERP study

Characterized by involuntary disruptions in fluency speech, adults who stutter (AWS) are different from normally fluent speakers (NFS) in speech-language processing indices of phonological, semantic, and syntactic information coding. However, the neural base of the prosodic information (i.e. prosodic boundary) processing in AWS is still elusive at this point. To investigate this question, Chinese temporarily ambiguous phrases (narrative-object/modifier-noun construction) were presented in pairs to AWS and NFS in both lexical judgment and structural judgment task by using structural priming paradigm. Results showed that both AWS and NFS produced prosodic priming in the two tasks, however, AWS were more sensitive to the priming than NFS in the midline. Besides, unlike the greater right hemisphere involvement of priming effect for NFS, AWS exhibited a left hemisphere asymmetry in the lateral areas. In addition, structural judgment task elicited stronger prosodic priming effect than lexical judgment task for both groups. These results indicate that the mode of prosodic priming for AWS is different from NFS, and the priming effect is influenced by the experimental task that participants completed.

Timing variability of sensorimotor integration during vocalization in individuals who stutter

Persistent developmental stuttering affects close to 1% of adults and is thought to be a problem of sensorimotor integration. Previous research has demonstrated that individuals who stutter respond differently to changes in their auditory feedback while speaking. Here we explore a number of changes that accompany alterations in the feedback of pitch during vocal production. Participants sustained the vowel /a/ while hearing on-line feedback of their own voice through headphones. In some trials, feedback was briefly shifted up or down by 100 cents to simulate a vocal production error. As previously shown, participants compensated for the auditory pitch change by altering their vocal production in the opposite direction of the shift. The average compensatory response was smaller for adults who stuttered than for adult controls. Detailed analyses revealed that adults who stuttered had fewer trials with a robust corrective response, and that within the trials showing compensation, the timing of their responses was more variable. These results support the idea that dysfunctional sensorimotor integration in stuttering is characterized by timing variability, reflecting reduced coupling of the auditory and speech motor systems.

Functional and Neuroanatomical Bases of Developmental Stuttering: Current Insights

Affecting 5% of all preschool-aged children and 1% of the general population, developmental stuttering-also called childhood-onset fluency disorder-is a complex, multifactorial neurodevelopmental disorder characterized by frequent disruption of the fluent flow of speech. Over the past two decades, neuroimaging studies of both children and adults who stutter have begun to provide significant insights into the neurobiological bases of stuttering. This review highlights convergent findings from this body of literature with a focus on functional and structural neuroimaging results that are supported by theoretically driven neurocomputational models of speech production. Updated views on possible mechanisms of stuttering onset and persistence, and perspectives on promising areas for future research into the mechanisms of stuttering, are discussed.

Trait related sensorimotor deficits in people who stutter: An EEG investigation of μ rhythm dynamics during spontaneous fluency

Stuttering is associated with compromised sensorimotor control (i.e., internal modeling) across the dorsal stream and oscillations of EEG mu (μ) rhythms have been proposed as reliable indices of anterior dorsal stream processing. The purpose of this study was to compare μ rhythm oscillatory activity between (PWS) and matched typically fluent speakers (TFS) during spontaneously fluent overt and covert speech production tasks. Independent component analysis identified bilateral μ components from 24/27 PWS and matched TFS that localized over premotor cortex. Time-frequency analysis of the left hemisphere μ clusters demonstrated significantly reduced μ-α and μ-β ERD (pCLUSTER < 0.05) in PWS across the time course of overt and covert speech production, while no group differences were found in the right hemisphere in any condition. Results were interpreted through the framework of State Feedback Control. They suggest that weak forward modeling and evaluation of sensory feedback across the time course of speech production characterizes the trait related sensorimotor impairment in PWS. This weakness is proposed to represent an underlying sensorimotor instability that may predispose the speech of PWS to breakdown.

Cortical dynamics of disfluency in adults who stutter

Stuttering is a disorder of speech production whose origins have been traced to the central nervous system. One of the factors that may underlie stuttering is aberrant neural miscommunication within the speech motor network. It is thus argued that disfluency (any interruption in the forward flow of speech) in adults who stutter (AWS) could be associated with anomalous cortical dynamics. Aberrant brain activity has been demonstrated in AWS in the absence of overt disfluency, but recording neural activity during disfluency is more challenging. The paradigm adopted here took an important step that involved overt reading of long and complex speech tokens under continuous EEG recording. Anomalies in cortical dynamics preceding disfluency were assessed by subtracting out neural activity for fluent utterances from their disfluent counterparts. Differences in EEG spectral power involving alpha, beta, and gamma bands, as well as anomalies in phase-coherence involving the gamma band, were observed prior to the production of the disfluent utterances. These findings provide novel evidence for compromised cortical dynamics that directly precede disfluency in AWS.

Anomalous network architecture of the resting brain in children who stutter

PURPOSE

We combined a large longitudinal neuroimaging dataset that includes children who do and do not stutter and a whole-brain network analysis in order to examine the intra- and inter-network connectivity changes associated with stuttering. Additionally, we asked whether whole brain connectivity patterns observed at the initial year of scanning could predict persistent stuttering in later years.

METHODS

A total of 224 high-quality resting state fMRI scans collected from 84 children (42 stuttering, 42 controls) were entered into an independent component analysis (ICA), yielding a number of distinct network connectivity maps ("components") as well as expression scores for each component that quantified the degree to which it is expressed for each child. These expression scores were compared between stuttering and control groups' first scans. In a second analysis, we examined whether the components that were most predictive of stuttering status also predicted persistence in stuttering.

RESULTS

Stuttering status, as well as stuttering persistence, were associated with aberrant network connectivity involving the default mode network and its connectivity with attention, somatomotor, and frontoparietal networks. The results suggest developmental alterations in the balance of integration and segregation of large-scale neural networks that support proficient task performance including fluent speech motor control.

CONCLUSIONS

This study supports the view that stuttering is a complex neurodevelopmental disorder and provides comprehensive brain network maps that substantiate past theories emphasizing the importance of considering situational, emotional, attentional and linguistic factors in explaining the basis for stuttering onset, persistence, and recovery.

A systematic literature review of neuroimaging research on developmental stuttering between 1995 and 2016

PURPOSE

Stuttering is a disorder that affects millions of people all over the world. Over the past two decades, there has been a great deal of interest in investigating the neural basis of the disorder. This systematic literature review is intended to provide a comprehensive summary of the neuroimaging literature on developmental stuttering. It is a resource for researchers to quickly and easily identify relevant studies for their areas of interest and enable them to determine the most appropriate methodology to utilize in their work. The review also highlights gaps in the literature in terms of methodology and areas of research.

METHODS

We conducted a systematic literature review on neuroimaging studies on developmental stuttering according to the PRISMA guidelines. We searched for articles in the pubmed database containing "stuttering" OR "stammering" AND either "MRI", "PET", "EEG", "MEG", "TMS"or "brain" that were published between 1995/​01/​01 and 2016/​01/​01.

RESULTS

The search returned a total of 359 items with an additional 26 identified from a manual search. Of these, there were a total of 111 full text articles that met criteria for inclusion in the systematic literature review. We also discuss neuroimaging studies on developmental stuttering published throughout 2016. The discussion of the results is organized first by methodology and second by population (i.e., adults or children) and includes tables that contain all items returned by the search.

CONCLUSIONS

There are widespread abnormalities in the structural architecture and functional organization of the brains of adults and children who stutter. These are evident not only in speech tasks, but also non-speech tasks. Future research should make greater use of functional neuroimaging and noninvasive brain stimulation, and employ structural methodologies that have greater sensitivity. Newly planned studies should also investigate sex differences, focus on augmenting treatment, examine moments of dysfluency and longitudinally or cross-sectionally investigate developmental trajectories in stuttering.

White matter tractography of the neural network for speech-motor control in children who stutter

Stuttering is a neurodevelopmental speech disorder with a phenotype characterized by speech sound repetitions, prolongations and silent blocks during speech production. Developmental stuttering affects 1% of the population and 5% of children. Neuroanatomical abnormalities in the major white matter tracts, including the arcuate fasciculus, corpus callosum, corticospinal, and frontal aslant tracts (FAT), are associated with the disorder in adults who stutter but are less well studied in children who stutter (CWS). We used deterministic tractography to assess the structural connectivity of the neural network for speech production in CWS and controls. CWS had higher fractional anisotropy and axial diffusivity in the right FAT than controls. Our findings support the involvement of the corticostriatal network early in persistent developmental stuttering.

EEG Mu (µ) rhythm spectra and oscillatory activity differentiate stuttering from non-stuttering adults

Stuttering is linked to sensorimotor deficits related to internal modeling mechanisms. This study compared spectral power and oscillatory activity of EEG mu (μ) rhythms between persons who stutter (PWS) and controls in listening and auditory discrimination tasks. EEG data were analyzed from passive listening in noise and accurate (same/different) discrimination of tones or syllables in quiet and noisy backgrounds. Independent component analysis identified left and/or right μ rhythms with characteristic alpha (α) and beta (β) peaks localized to premotor/motor regions in 23 of 27 people who stutter (PWS) and 24 of 27 controls. PWS produced μ spectra with reduced β amplitudes across conditions, suggesting reduced forward modeling capacity. Group time-frequency differences were associated with noisy conditions only. PWS showed increased μ-β desynchronization when listening to noise and early in discrimination events, suggesting evidence of heightened motor activity that might be related to forward modeling deficits. PWS also showed reduced μ-α synchronization in discrimination conditions, indicating reduced sensory gating. Together these findings indicate spectral and oscillatory analyses of μ rhythms are sensitive to stuttering. More specifically, they can reveal stuttering-related sensorimotor processing differences in listening and auditory discrimination that also may be influenced by basal ganglia deficits.

Research about suppression effect and auditory processing in individuals who stutter

Purpose

To verify the auditory processing abilities and occurrence of the suppression effect of Otoacoustic Emissions (OAE) in individuals who stutter.

Methods

The study sample comprised 15 adult individuals who stutter, aged 18-40 years, with stuttering severity ranging from mild to severe, paired according to gender, age, and schooling with individuals without speech complaint or disorder. All participants underwent conventional clinical evaluation, specific stuttering assessment, and basic (audiometry, imitanciometry, and measurement of acoustic reflexes) and specific (auditory processing evaluation and measurement of suppression effect of OAEs) audiological assessments. Data were statistically analyzed with application of the Fisher's Exact Test and the Mann-Whitney Test.

Results

The group of individuals who stutter (Study Group - SG) presented higher incidence of auditory processing disorders. The auditory processing assessments used to differentiate the groups of stutterers and non-stutterers (Control Group - CG) were the Nonverbal Dichotic Test and the Frequency Pattern Test. The SG presented higher incidence of absence of suppression effect of OAEs, indicating abnormal functioning of the efferent medial olivocochlear system.

Conclusion

The auditory processing abilities investigated in this study differentiate individuals who stutter from non-stutterers, with greater changes in the first. Functioning of the efferent medial olivocochlear system showed a deficit in stutterers, indicating difficulties in auditory discrimination, especially in the presence of noise.

Dynamic Estimation of the Auditory Temporal Response Function From MEG in Competing-Speaker Environments

OBJECTIVE

A central problem in computational neuroscience is to characterize brain function using neural activity recorded from the brain in response to sensory inputs with statistical confidence. Most of existing estimation techniques, such as those based on reverse correlation, exhibit two main limitations: first, they are unable to produce dynamic estimates of the neural activity at a resolution comparable with that of the recorded data, and second, they often require heavy averaging across time as well as multiple trials in order to construct statistical confidence intervals for a precise interpretation of data. In this paper, we address the above-mentioned issues for estimating auditory temporal response function (TRF) as a parametric computational model for selective auditory attention in competing-speaker environments.

METHODS

The TRF is a sparse kernel which regresses auditory MEG data with respect to the envelopes of the speech streams. We develop an efficient estimation technique by exploiting the sparsity of the TRF and adopting an ℓ₁-regularized least squares estimator which is capable of producing dynamic TRF estimates as well as confidence intervals at sampling resolution from single-trial MEG data.

RESULTS

We evaluate the performance of our proposed estimator using evoked MEG responses from the human brain in an auditory attention experiment with two competing speakers. The TRFs are estimated dynamically over time using the proposed technique with multisecond resolution, which is a significant improvement over previous results with a temporal resolution of the order of a minute.

CONCLUSION

Application of our method to MEG data reveals a precise characterization of the modulation of M50 and M100 evoked responses with respect to the attentional state of the subject at multisecond resolution.

SIGNIFICANCE

Our proposed estimation technique provides a high resolution real-time attention decoding framework in multispeaker environments with potential application in smart hearing aid technology.

Cortical activity during cued picture naming predicts individual differences in stuttering frequency

OBJECTIVE

Developmental stuttering is characterized by fluent speech punctuated by stuttering events, the frequency of which varies among individuals and contexts. Most stuttering events occur at the beginning of an utterance, suggesting neural dynamics associated with stuttering may be evident during speech preparation.

METHODS

This study used EEG to measure cortical activity during speech preparation in men who stutter, and compared the EEG measures to individual differences in stuttering rate as well as to a fluent control group. Each trial contained a cue followed by an acoustic probe at one of two onset times (early or late), and then a picture. There were two conditions: a speech condition where cues induced speech preparation of the picture's name and a control condition that minimized speech preparation.

RESULTS

Across conditions stuttering frequency correlated to cue-related EEG beta power and auditory ERP slow waves from early onset acoustic probes.

CONCLUSIONS

The findings reveal two new cortical markers of stuttering frequency that were present in both conditions, manifest at different times, are elicited by different stimuli (visual cue, auditory probe), and have different EEG responses (beta power, ERP slow wave).

SIGNIFICANCE

The cue-target paradigm evoked brain responses that correlated to pre-experimental stuttering rate.

Dissociations among linguistic, cognitive, and auditory-motor neuroanatomical domains in children who stutter

The onset of developmental stuttering typically occurs between 2 to 4 years of age, coinciding with a period of rapid development in speech, language, motor and cognitive domains. Previous studies have reported generally poorer performance and uneven, or "dissociated" development across speech and language domains in children who stutter (CWS) relative to children who do not stutter (CWNS) (Anderson, Pellowski, & Conture, 2005). The aim of this study was to replicate and expand previous findings by examining whether CWS exhibit dissociated development across speech-language, cognitive, and motor domains that are also reflected in measures of neuroanatomical development. Participants were 66CWS (23 females) and 53CWNS (26 females) ranging from 3 to 10 years. Standardized speech, language, cognitive, and motor skills measures, and fractional anisotropy (FA) values derived from diffusion tensor imaging from speech relevant "dorsal auditory" left perisylvian areas (Hickok & Poeppel, 2007) were analyzed using a correlation-based statistical procedure (Coulter, Anderson, & Conture, 2009) that quantified dissociations across domains. Overall, CWS scored consistently lower on speech, language, cognitive and motor measures, and exhibited dissociated development involving these same measures and white matter neuroanatomical indices relative to CWNS. Boys who stutter exhibited a greater number of dissociations compared to girls who stutter. Results suggest a subgroup of CWS may have incongruent development across multiple domains, and the resolution of this imbalance may be a factor in recovery from stuttering.

Beyond production: Brain responses during speech perception in adults who stutter

Developmental stuttering is a speech disorder that disrupts the ability to produce speech fluently. While stuttering is typically diagnosed based on one's behavior during speech production, some models suggest that it involves more central representations of language, and thus may affect language perception as well. Here we tested the hypothesis that developmental stuttering implicates neural systems involved in language perception, in a task that manipulates comprehensibility without an overt speech production component. We used functional magnetic resonance imaging to measure blood oxygenation level dependent (BOLD) signals in adults who do and do not stutter, while they were engaged in an incidental speech perception task. We found that speech perception evokes stronger activation in adults who stutter (AWS) compared to controls, specifically in the right inferior frontal gyrus (RIFG) and in left Heschl's gyrus (LHG). Significant differences were additionally found in the lateralization of response in the inferior frontal cortex: AWS showed bilateral inferior frontal activity, while controls showed a left lateralized pattern of activation. These findings suggest that developmental stuttering is associated with an imbalanced neural network for speech processing, which is not limited to speech production, but also affects cortical responses during speech perception.

Speech preparation in adults with persistent developmental stuttering

Motor efference copy conveys movement information to sensory areas before and during vocalization. We hypothesized speech preparation would modulate auditory processing, via motor efference copy, differently in men who stutter (MWS) vs. fluent adults. Participants (n=12/group) had EEG recorded during a cue-target paradigm with two conditions: speech which allowed for speech preparation, while a control condition did not. Acoustic stimuli probed auditory responsiveness between the cue and target. MWS had longer vocal reaction times (p<0.01) when the cue-target differed (10% of trials), suggesting a difficulty of rapidly updating their speech plans. Acoustic probes elicited a negative slow wave indexing motor efference copy that was smaller in MWS vs. fluent adults (p<0.03). Current density responses in MWS showed smaller left prefrontal responses and auditory responses that were delayed and correlated to stuttering rate. Taken together, the results provide insight into the cortical mechanisms underlying atypical speech planning and dysfluencies in MWS.

Context-dependent impact of presuppositions on early magnetic brain responses during speech perception

Discourse structure enables us to generate expectations based upon linguistic material that has already been introduced. The present magnetoencephalography (MEG) study addresses auditory perception of test sentences in which discourse coherence was manipulated by using presuppositions (PSP) that either correspond or fail to correspond to items in preceding context sentences with respect to uniqueness and existence. Context violations yielded delayed auditory M50 and enhanced auditory M200 cross-correlation responses to syllable onsets within an analysis window of 1.5s following the PSP trigger words. Furthermore, discourse incoherence yielded suppression of spectral power within an expanded alpha band ranging from 6 to 16Hz. This effect showed a bimodal temporal distribution, being significant in an early time window of 0.0-0.5s following the PSP trigger and a late interval of 2.0-2.5s. These findings indicate anticipatory top-down mechanisms interacting with various aspects of bottom-up processing during speech perception.

Neural systems mediating processing of sound units of language distinguish recovery versus persistence in stuttering

BACKGROUND

Developmental stuttering is a multi-factorial disorder. Measures of neural activity while children processed the phonological (language sound unit) properties of words have revealed neurodevelopmental differences between fluent children and those who stutter. However, there is limited evidence to show whether the neural bases of phonological processing can be used to identify stuttering recovery status. As an initial step, we aimed to determine if differences in neural activity during phonological processing could aid in distinguishing children who had recovered from stuttering and those whose stuttering persisted.

METHODS

We examined neural activity mediating phonological processing in forty-three 7-8 year old children. Groups included children who had recovered from stuttering (CWS-Rec), those whose stuttering persisted (CWS-Per), and children who did not stutter (CWNS). All children demonstrated normal non-verbal intelligence and language skills. Electroencephalograms were recorded as the children listened to pairs of pseudo-words (primes-targets) that either rhymed or did not. Behavioral rhyme judgments along with peak latency and mean amplitude of the N400s elicited by prime and target stimuli were examined.

RESULTS

All the groups were very accurate in their rhyme judgments and displayed a typical ERP rhyme effect, characterized by increased N400 amplitudes over central parietal sites for nonrhyming targets compared to rhyming targets. However, over anterior electrode sites, an earlier onset of the N400 for rhyming compared to non-rhyming targets, indexing phonological segmentation and rehearsal, was observed in the CWNS and CWS-Rec groups. This effect occurred bilaterally for the CWNS, was greater over the right hemisphere in the CWS-Rec, and was absent in the CWS-Per.

CONCLUSIONS

These results are the first to show that differences in ERPs reflecting phonological processing are marked by atypical lateralization in childhood even after stuttering recovery and more pronounced atypical neural patterns for the children whose stuttering persisted. Despite comparable language and phonological skills as revealed by standardized tests, the neural activity mediating phonological segmentation and rehearsal differentiated 7-8 year old children whose stuttering persisted from those who had recovered from stuttering and typically developing peers.

Modulation of auditory processing during speech movement planning is limited in adults who stutter

Stuttering is associated with atypical structural and functional connectivity in sensorimotor brain areas, in particular premotor, motor, and auditory regions. It remains unknown, however, which specific mechanisms of speech planning and execution are affected by these neurological abnormalities. To investigate pre-movement sensory modulation, we recorded 12 stuttering and 12 nonstuttering adults' auditory evoked potentials in response to probe tones presented prior to speech onset in a delayed-response speaking condition vs. no-speaking control conditions (silent reading; seeing nonlinguistic symbols). Findings indicate that, during speech movement planning, the nonstuttering group showed a statistically significant modulation of auditory processing (reduced N1 amplitude) that was not observed in the stuttering group. Thus, the obtained results provide electrophysiological evidence in support of the hypothesis that stuttering is associated with deficiencies in modulating the cortical auditory system during speech movement planning. This specific sensorimotor integration deficiency may contribute to inefficient feedback monitoring and, consequently, speech dysfluencies.

The trajectory of gray matter development in Broca's area is abnormal in people who stutter

The acquisition and mastery of speech-motor control requires years of practice spanning the course of development. People who stutter often perform poorly on speech-motor tasks thereby calling into question their ability to establish the stable neural motor programs required for masterful speech-motor control. There is evidence to support the assertion that these neural motor programs are represented in the posterior part of Broca’s area, specifically the left pars opercularis. Consequently, various theories of stuttering causation posit that the disorder is related to a breakdown in the formation of the neural motor programs for speech early in development and that this breakdown is maintained throughout life. To date, no study has examined the potential neurodevelopmental signatures of the disorder across pediatric and adult populations. The current study aimed to fill this gap in our knowledge. We hypothesized that the developmental trajectory of cortical thickness in people who stutter would differ across the lifespan in the left pars opercularis relative to a group of control participants. We collected structural magnetic resonance images from 116 males (55 people who stutter) ranging in age from 6 to 48 years old. Differences in cortical thickness across ages and between patients and controls were investigated in 30 brain regions previously implicated in speech-motor control. An interaction between age and group was found for the left pars opercularis only. In people who stutter, the pars opercularis did not demonstrate the typical maturational pattern of gradual gray matter thinning with age across the lifespan that we observed in control participants. In contrast, the developmental trajectory of gray matter thickness in other regions of interest within the neural network for speech-motor control was similar for both groups. Our findings indicate that the developmental trajectory of gray matter in left pars opercularis is abnormal in people who stutter.

Sensory-motor networks involved in speech production and motor control: an fMRI study

Speaking is one of the most complex motor behaviors developed to facilitate human communication. The underlying neural mechanisms of speech involve sensory-motor interactions that incorporate feedback information for online monitoring and control of produced speech sounds. In the present study, we adopted an auditory feedback pitch perturbation paradigm and combined it with functional magnetic resonance imaging (fMRI) recordings in order to identify brain areas involved in speech production and motor control. Subjects underwent fMRI scanning while they produced a steady vowel sound /a/ (speaking) or listened to the playback of their own vowel production (playback). During each condition, the auditory feedback from vowel production was either normal (no perturbation) or perturbed by an upward (+600 cents) pitch-shift stimulus randomly. Analysis of BOLD responses during speaking (with and without shift) vs. rest revealed activation of a complex network including bilateral superior temporal gyrus (STG), Heschl's gyrus, precentral gyrus, supplementary motor area (SMA), Rolandic operculum, postcentral gyrus and right inferior frontal gyrus (IFG). Performance correlation analysis showed that the subjects produced compensatory vocal responses that significantly correlated with BOLD response increases in bilateral STG and left precentral gyrus. However, during playback, the activation network was limited to cortical auditory areas including bilateral STG and Heschl's gyrus. Moreover, the contrast between speaking vs. playback highlighted a distinct functional network that included bilateral precentral gyrus, SMA, IFG, postcentral gyrus and insula. These findings suggest that speech motor control involves feedback error detection in sensory (e.g. auditory) cortices that subsequently activate motor-related areas for the adjustment of speech parameters during speaking.

Neurodevelopment for syntactic processing distinguishes childhood stuttering recovery versus persistence

BACKGROUND

Characterized by the presence of involuntary speech disfluencies, developmental stuttering is a neurodevelopmental disorder of atypical speech-motor coordination. Although the etiology of stuttering is multifactorial, language development during early childhood may influence both the onset of the disorder and the likelihood of recovery. The purpose of this study was to determine whether differences in neural indices mediating language processing are associated with persistence or recovery in school-age children who stutter.

METHODS

Event-related brain potentials (ERPs) were obtained from 31 6-7-year-olds, including nine children who do not stutter (CWNS), 11 children who had recovered from stuttering (CWS-Rec), and 11 children who persisted in stuttering (CWS-Per), matched for age, and all with similar socioeconomic status, nonverbal intelligence, and language ability. We examined ERPs elicited by semantic and syntactic (phrase structure) violations within an auditory narrative consisting of English and Jabberwocky sentences. In Jabberwocky sentences, content words were replaced with pseudowords to limit semantic context. A mixed effects repeated measures analysis of variance (ANOVA) was computed for ERP components with four within-subject factors, including condition, hemisphere, anterior/posterior distribution, and laterality.

RESULTS

During the comprehension of English sentences, ERP activity mediating semantic and syntactic (phrase structure) processing did not distinguish CWS-Per, CWS-Rec, and CWNS. Semantic violations elicited a qualitatively similar N400 component across groups. Phrase structure violations within English sentences also elicited a similar P600 component in all groups. However, identical phrase structure violations within Jabberwocky sentences elicited a P600 in CWNS and CWS-Rec, but an N400-like effect in CWS-Per.

CONCLUSIONS

The distinguishing neural patterns mediating syntactic, but not semantic, processing provide evidence that specific brain functions for some aspects of language processing may be associated with stuttering persistence. Unlike CWS-Rec and CWNS, the lack of semantic context in Jabberwocky sentences seemed to affect the syntactic processing strategies of CWS-Per, resulting in the elicitation of semantically based N400-like activity during syntactic (phrase structure) violations. This vulnerability suggests neural mechanisms associated with the processing of syntactic structure may be less mature in 6-7-year-old children whose stuttering persisted compared to their fluent or recovered peers.

Atypical central auditory speech-sound discrimination in children who stutter as indexed by the mismatch negativity

PURPOSE

Recent theoretical conceptualizations suggest that disfluencies in stuttering may arise from several factors, one of them being atypical auditory processing. The main purpose of the present study was to investigate whether speech sound encoding and central auditory discrimination, are affected in children who stutter (CWS).

METHODS

Participants were 10 CWS, and 12 typically developing children with fluent speech (TDC). Event-related potentials (ERPs) for syllables and syllable changes [consonant, vowel, vowel-duration, frequency (F0), and intensity changes], critical in speech perception and language development of CWS were compared to those of TDC.

RESULTS

There were no significant group differences in the amplitudes or latencies of the P1 or N2 responses elicited by the standard stimuli. However, the Mismatch Negativity (MMN) amplitude was significantly smaller in CWS than in TDC. For TDC all deviants of the linguistic multifeature paradigm elicited significant MMN amplitudes, comparable with the results found earlier with the same paradigm in 6-year-old children. In contrast, only the duration change elicited a significant MMN in CWS.

CONCLUSIONS

The results showed that central auditory speech-sound processing was typical at the level of sound encoding in CWS. In contrast, central speech-sound discrimination, as indexed by the MMN for multiple sound features (both phonetic and prosodic), was atypical in the group of CWS. Findings were linked to existing conceptualizations on stuttering etiology.

EDUCATIONAL OBJECTIVES

The reader will be able (a) to describe recent findings on central auditory speech-sound processing in individuals who stutter, (b) to describe the measurement of auditory reception and central auditory speech-sound discrimination, (c) to describe the findings of central auditory speech-sound discrimination, as indexed by the mismatch negativity (MMN), in children who stutter.

Preschool speech articulation and nonword repetition abilities may help predict eventual recovery or persistence of stuttering

PURPOSE

In preschool children, we investigated whether expressive and receptive language, phonological, articulatory, and/or verbal working memory proficiencies aid in predicting eventual recovery or persistence of stuttering.

METHODS

Participants included 65 children, including 25 children who do not stutter (CWNS) and 40 who stutter (CWS) recruited at age 3;9-5;8. At initial testing, participants were administered the Test of Auditory Comprehension of Language, 3rd edition (TACL-3), Structured Photographic Expressive Language Test, 3rd edition (SPELT-3), Bankson-Bernthal Test of Phonology-Consonant Inventory subtest (BBTOP-CI), Nonword Repetition Test (NRT; Dollaghan & Campbell, 1998), and Test of Auditory Perceptual Skills-Revised (TAPS-R) auditory number memory and auditory word memory subtests. Stuttering behaviors of CWS were assessed in subsequent years, forming groups whose stuttering eventually persisted (CWS-Per; n=19) or recovered (CWS-Rec; n=21). Proficiency scores in morphosyntactic skills, consonant production, verbal working memory for known words, and phonological working memory and speech production for novel nonwords obtained at the initial testing were analyzed for each group.

RESULTS

CWS-Per were less proficient than CWNS and CWS-Rec in measures of consonant production (BBTOP-CI) and repetition of novel phonological sequences (NRT). In contrast, receptive language, expressive language, and verbal working memory abilities did not distinguish CWS-Rec from CWS-Per. Binary logistic regression analysis indicated that preschool BBTOP-CI scores and overall NRT proficiency significantly predicted future recovery status.

CONCLUSION

Results suggest that phonological and speech articulation abilities in the preschool years should be considered with other predictive factors as part of a comprehensive risk assessment for the development of chronic stuttering.

EDUCATIONAL OBJECTIVES

At the end of this activity the reader will be able to: (1) describe the current status of nonlinguistic and linguistic predictors for recovery and persistence of stuttering; (2) summarize current evidence regarding the potential value of consonant cluster articulation and nonword repetition abilities in helping to predict stuttering outcome in preschool children; (3) discuss the current findings in relation to potential implications for theories of developmental stuttering; (4) discuss the current findings in relation to potential considerations for the evaluation and treatment of developmental stuttering.

Absolute and relative reliability of percentage of syllables stuttered and severity rating scales

PURPOSE

Percentage of syllables stuttered (%SS) and severity rating (SR) scales are measures in common use to quantify stuttering severity and its changes during basic and clinical research conditions. However, their reliability has not been assessed with indices measuring both relative and absolute reliability. This study was designed to provide such information. Relative reliability deals with the rank order of participants in a sample, whereas absolute reliability measures the closeness of scores to one other and to a hypothetical true score.

METHOD

Eighty-seven adult participants who stutter received a 10-min unscheduled telephone call. Three experienced judges measured %SS and also used a 9-point SR scale to measure stuttering severity from recordings of the telephone calls.

RESULTS

Relative intrajudge and interjudge reliability were satisfactory for both scales. However, absolute intrajudge and interjudge reliability were not satisfactory. Results showed that paired-judge SR and %SS procedures improved absolute reliability compared with single-judge measures. Additionally, the paired-judge procedure improved relative reliability from high to very high levels.

CONCLUSION

Measurement of group changes of stuttering severity can be done in research contexts using either %SS or SR. However, for detecting changes within individuals using such measures, a paired-judge procedure is a more reliable method.

Research updates in neuroimaging studies of children who stutter

In the past two decades, neuroimaging investigations of stuttering have led to important discoveries of structural and functional brain differences in people who stutter, providing significant clues to the neurological basis of stuttering. One major limitation, however, has been that most studies so far have only examined adults who stutter, whose brain and behavior likely would have adopted compensatory reactions to their stuttering; these confounding factors have made interpretations of the findings difficult. Developmental stuttering is a neurodevelopmental condition, and like many other neurodevelopmental disorders, stuttering is associated with an early childhood onset of symptoms and greater incidence in males relative to females. More recent studies have begun to examine children who stutter using various neuroimaging techniques that allow examination of functional neuroanatomy and interaction of major brain areas that differentiate children who stutter compared with age-matched controls. In this article, I review these more recent neuroimaging investigations of children who stutter, in the context of what we know about typical brain development, neuroplasticity, and sex differences relevant to speech and language development. Although the picture is still far from complete, these studies have potential to provide information that can be used as early objective markers, or prognostic indicators, for persistent stuttering in the future. Furthermore, these studies are the first steps in finding potential neural targets for novel therapies that may involve modulating neuroplastic growth conducive to developing and maintaining fluent speech, which can be applied to treatment of young children who stutter.

Impaired timing adjustments in response to time-varying auditory perturbation during connected speech production in persons who stutter

Auditory feedback (AF), the speech signal received by a speaker's own auditory system, contributes to the online control of speech movements. Recent studies based on AF perturbation provided evidence for abnormalities in the integration of auditory error with ongoing articulation and phonation in persons who stutter (PWS), but stopped short of examining connected speech. This is a crucial limitation considering the importance of sequencing and timing in stuttering. In the current study, we imposed time-varying perturbations on AF while PWS and fluent participants uttered a multisyllabic sentence. Two distinct types of perturbations were used to separately probe the control of the spatial and temporal parameters of articulation. While PWS exhibited only subtle anomalies in the AF-based spatial control, their AF-based fine-tuning of articulatory timing was substantially weaker than normal, especially in early parts of the responses, indicating slowness in the auditory-motor integration for temporal control.