Persons Who Stutter Research Articles

Utility of virtual reality environments to examine physiological reactivity and subjective distress in adults who stutter

PurposeVirtual reality environments (VREs) allow for immersion in speaking environments that mimic real-life interactions while maintaining researcher control. VREs have been used successfully to engender arousal in other disorders. The purpose of this study was to investigate the utility of virtual reality environments to examine physiological reactivity and subjective ratings of distress in persons who stutter (PWS). MethodSubjective and objective measures of arousal were collected from 10PWS during four-minute speeches to a virtual audience and to a virtual empty room. ResultsStuttering frequency and physiological measures (skin conductance level and heart rate) did not differ across speaking conditions, but subjective ratings of distress were significantly higher in the virtual audience condition compared to the virtual empty room. ConclusionVREs have utility in elevating subjective ratings of distress in PWS. VREs have the potential to be useful tools for practicing treatment targets in a safe, controlled, and systematic manner.

Backward masking abilities for speech and tones in persons who stutter

We examined eight persons who stutter (PWS) and eight carefully matched adult, control participants for their ability to identify vowel-consonant (VC) syllables and to detect tones in a backward masking paradigm. Speech scores (percent correct) were obtained in quiet and in conditions with a fixed-level broadband masker with a delay of 0 ms and 300 ms. Tonal thresholds (1000 Hz) were obtained using an adaptive procedure in quiet and with the same masker delays as in the speech conditions. The results revealed significantly poorer performance for PWS for all of the speech conditions, including the quiet condition. Tonal thresholds in quiet and for the condition with a 300 ms delay were identical for the two groups, but, on average, the trend was for higher masked thresholds for PWS than for the control group in the 0 ms condition. The poorer speech results are consistent with the idea that PWS may have less distinct representations of phonemic categories that are revealed in a VC task that lacks a language...

An Overview of Facilities Providing Clinical Services for Persons Who Stutter in Kuwait

Presently, no clear picture is available about the facilities providing clinical services for persons who stutter (PWS) in Kuwait. This information is crucial for any awareness program to be established in the future. The purpose of this study was to identify clinical facilities and speech-language personnel that provide services for PWS in Kuwait. Participants consisted of 21 clinical directors of governmental medical centers, non-profit clinics, and private clinics as well as department heads of governmental school clinics where speech-language services were provided. Participants were interviewed regarding the availability of speech-language services within their centers and whether or not PWS receive services. The results revealed that four out of five governmental medical centers with a total of 32 speech-language pathologists (SLPs) provided services for PWS. Additionally, 12 schools of special education were found to have 62 SLPs on their staff providing fluency services for students. Finally, two stand-alone private clinics and one non-profit clinic provided services for PWS. Results indicated an overall shortage of SLPs in the country, especially in medical settings. This study sets the foundation for a series of future studies investigating the type and quality of stuttering services provided by the identified facilities in Kuwait.

Perceptions of Persons who Stutter before and after Attending Support Group Meetings

The authors surveyed members of a stuttering support group to assess the perceptions of persons who stutter (PWS) before and after attending support group meetings as well as factors that may be involved in sustainability of support groups for PWS. The group leadership incorporated into meetings, principles that would be most salient to helping PWS in a support group environment. The group integrated many of the 11 key therapeutic principles proposed by Yalom (1995) for effective group counselling and group therapy. Preliminary data indicate that involvement in the support group resulted in more positive feelings about being called a PWS and being a PWS and lessened the impact that stuttering has on a member's life. Participants reported that they gained hope, confidence, self-esteem, and a positive outlook as a result of attending support group meetings. Overall, it appears that the views of the respondents were consistent with several of Yalom's principles. The members believed that their involvement in meetings led them to positively change their views about stuttering and their own acceptance of their stuttering.

Near-Infrared Spectroscopy Technology in Typically Fluent Speakers and Persons who Stutter

Near-infrared spectroscopy (NIRS) is a biomedical optical imaging technique that is used to measure real-time functional brain activity. NIRS uses non-invasive infrared light to measure oxy-, de-oxy, and total hemoglobin concentration at the surface of the cerebral cortex. Hemoglobin concentration is monitored through the use of light scattering and tissue absorption. NIRS is advantageous over other techniques (e.g., EEG, MRI, PET etc.) because it does not utilize harmful radiation or an extrinsic contrast agent. It is also portable and is a low cost technology to administer. NIRS can also be used with infants, young children, and adults. Since its discovery, NIRS has been used to study Alzheimer's disease, verbal fluency, language processing, epilepsy, frontal lateralization in speech tasks, cerebral hemodynamics, visual stimulation, odor stimulation, chronic schizophrenia, and other conditions. We have used NIRS to measure hemoglobin changes in typically fluent speakers (TFS) and persons who stutter (PWS). Our NIRS device has 16 sources and 24 detectors to measure haemoglobin concentration changes during speech and non-speech tasks for TFS and PWS. Our participants ranged in age from 10 to young adulthood. Measurements were taken during three conditions: Speakers were asked to read out loud, to engage in spontaneous speech, and to sit for a rest period. The purpose of this study was to determine whether there were haemoglobin concentration changes in TFS and PWS while they engaged in speech and non-speech tasks. Initial results indicate that speech tasks caused hemoglobin concentration changes. A more in-depth analysis of our technology and pilot data will be presented.

Real enough: using virtual public speaking environments to evoke feelings and behaviors targeted in stuttering assessment and treatment.

Virtual reality environments (VREs) are computer-generated, 3-dimensional worlds that allow users to experience situations similar to those encountered in the real world. The purpose of this study was to investigate VREs for potential use in assessing and treating persons who stutter (PWS) by determining the extent to which PWS's affective, behavioral, and cognitive measures in a VRE correlate with those same measures in a similar live environment. Ten PWS delivered speeches-first to a live audience and, on another day, to 2 virtual audiences (neutral and challenging audiences). Participants completed standard tests of communication apprehension and confidence prior to each condition, and frequency of stuttering was measured during each speech. Correlational analyses revealed significant, positive correlations between virtual and live conditions for affective and cognitive measures as well as for frequency of stuttering. These findings suggest that virtual public speaking environments engender affective, behavioral, and cognitive reactions in PWS that correspond to those experienced in the real world. Therefore, the authentic, safe, and controlled environments provided by VREs may be useful for stuttering assessment and treatment.

Stuttering, induced fluency, and natural fluency: A hierarchical series of activation likelihood estimation meta-analyses

Developmental stuttering is a speech disorder most likely due to a heritable form of developmental dysmyelination impairing the function of the speech-motor system. Speech-induced brain-activation patterns in persons who stutter (PWS) are anomalous in various ways; the consistency of these aberrant patterns is a matter of ongoing debate. Here, we present a hierarchical series of coordinate-based meta-analyses addressing this issue. Two tiers of meta-analyses were performed on a 17-paper dataset (202 PWS; 167 fluent controls). Four large-scale (top-tier) meta-analyses were performed, two for each subject group (PWS and controls). These analyses robustly confirmed the regional effects previously postulated as “neural signatures of stuttering” (Brown, Ingham, Ingham, Laird, & Fox, 2005) and extended this designation to additional regions. Two smaller-scale (lower-tier) meta-analyses refined the interpretation of the large-scale analyses: (1) a between-group contrast targeting differences between PWS and controls (stuttering trait); and (2) a within-group contrast (PWS only) of stuttering with induced fluency (stuttering state).

Retention of Implicit Sequence Learning in Persons Who Stutter and Persons With Parkinson's Disease

ABSTRACT. The authors investigated the retention of implicit sequence learning in 14 persons with Parkinson's disease (PPD), 14 persons who stutter (PWS), and 14 control participants. Participants completed a nonsense syllable serial reaction time task in a 120-min session. Participants named aloud 4 syllables in response to 4 visual stimuli. The syllables formed a repeating 8-item sequence not made known to participants. After 1 week, participants completed a 60-min retention session that included an explicit learning questionnaire and a sequence generation task. PPD showed retention of general learning equivalent to controls but PWS's reaction times were significantly slower on early trials of the retention test relative to other groups. Controls showed implicit learning during the initial session that was retained on the retention test. In contrast, PPD and PWS did not demonstrate significant implicit learning until the retention test suggesting intact, but delayed, learning and retention of implicit sequencing skills. All groups demonstrated similar limited explicit sequence knowledge. Performance differences between PWS and PPD relative to controls during the initial session and on early retention trials indicated possible dysfunction of the cortico-striato-thalamo-cortical loop. The etiological implications for stuttering, and clinical implications for both populations, of this dysfunction are discussed.

Functional connectivity changes in adults with developmental stuttering: a preliminary study using quantitative electro-encephalography.

Introduction: Stuttering is defined as speech characterized by verbal dysfluencies, but should not be seen as an isolated speech disorder, but as a generalized sensorimotor timing deficit due to impaired communication between speech related brain areas. Therefore we focused on resting state brain activity and functional connectivity.Method: We included 11 patients with developmental stuttering and 11 age matched controls. To objectify stuttering severity and the impact on quality of life (QoL), we used the Dutch validated Test for Stuttering Severity-Readers (TSS-R) and the Overall Assessment of the Speaker’s Experience of Stuttering (OASES), respectively. Furthermore, we used standardized low resolution brain electromagnetic tomography (sLORETA) analyses to look at resting state activity and functional connectivity differences and their correlations with the TSS-R and OASES.Results: No significant results could be obtained when looking at neural activity, however significant alterations in resting state functional connectivity could be demonstrated between persons who stutter (PWS) and fluently speaking controls, predominantly interhemispheric, i.e., a decreased functional connectivity for high frequency oscillations (beta and gamma) between motor speech areas (BA44 and 45) and the contralateral premotor (BA6) and motor (BA4) areas. Moreover, a positive correlation was found between functional connectivity at low frequency oscillations (theta and alpha) and stuttering severity, while a mixed increased and decreased functional connectivity at low and high frequency oscillations correlated with QoL.Discussion: PWS are characterized by decreased high frequency interhemispheric functional connectivity between motor speech, premotor and motor areas in the resting state, while higher functional connectivity in the low frequency bands indicates more severe speech disturbances, suggesting that increased interhemispheric and right sided functional connectivity is maladaptive.

Compilation of a preliminary checklist for the differential diagnosis of neurogenic stuttering.

Neurogenic stuttering (NS) is the most frequently occurring acquired form of stuttering in children and adults. This form of stuttering is primarily caused by neurological incidents. Owing to controversies with regard to similarities between developmental stuttering (DS) and NS symptomatology, differential diagnosis is problematic. Differential diagnosis will guide the appropriate management of persons who stutter (PWS). The aim of this study was to describe and highlight the characteristics of NS in order to compile a preliminary checklist for accurate diagnosis and intervention. An explorative, applied mixed method, multiple case study research design was followed. Purposive sampling was used to select four participants. A comprehensive assessment battery was compiled for data collection. The results revealed a distinct pattern of core stuttering behaviours in NS, although discrepancies existed regarding stuttering severity and frequency. It was also found that DS and NS can co-occur. The case history and the core stuttering pattern are important considerations during differential diagnosis, as these are the only consistent characteristics in people with NS. It is unlikely that all the symptoms of NS are present in an individual. The researchers scrutinised the findings of this study and the findings of previous literature to compile a potentially workable checklist.

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.

Diffusion imaging of cerebral white matter in persons who stutter: evidence for network-level anomalies.

Deficits in brain white matter have been a main focus of recent neuroimaging studies on stuttering. However, no prior study has examined brain connectivity on the global level of the cerebral cortex in persons who stutter (PWS). In the current study, we analyzed the results from probabilistic tractography between regions comprising the cortical speech network. An anatomical parcellation scheme was used to define 28 speech production-related ROIs in each hemisphere. We used network-based statistic (NBS) and graph theory to analyze the connectivity patterns obtained from tractography. At the network-level, the probabilistic corticocortical connectivity from the PWS group were significantly weaker than that from persons with fluent speech (PFS). NBS analysis revealed significant components in the bilateral speech networks with negative correlations with stuttering severity. To facilitate comparison with previous studies, we also performed tract-based spatial statistics (TBSS) and regional fractional anisotropy (FA) averaging. Results from tractography, TBSS and regional FA averaging jointly highlight the importance of several regions in the left peri-Rolandic sensorimotor and premotor areas, most notably the left ventral premotor cortex (vPMC) and middle primary motor cortex, in the neuroanatomical basis of stuttering.

Systematic studies of modified vocalization: the effect of speech rate on speech production measures during metronome‐paced speech in persons who stutter

Metronome-paced speech results in the elimination, or substantial reduction, of stuttering moments. The cause of fluency during this fluency-inducing condition is unknown. Several investigations have reported changes in speech pattern characteristics from a control condition to a metronome-paced speech condition, but failure to control speech rate between conditions limits our ability to determine if the changes were necessary for fluency. This study examined the effect of speech rate on several speech production variables during one-syllable-per-beat metronomic speech in order to determine changes that may be important for fluency during this fluency-inducing condition. Thirteen persons who stutter (PWS), aged 18-62 years, completed a series of speaking tasks. Several speech production variables were compared between conditions produced at different metronome beat rates, and between a control condition and a metronome-paced speech condition produced at a rate equal to the control condition. Vowel duration, voice onset time, pressure rise time and phonated intervals were significantly impacted by metronome beat rate. Voice onset time and the percentage of short (30-100 ms) phonated intervals significantly decreased from the control condition to the equivalent rate metronome-paced speech condition. A reduction in the percentage of short phonated intervals may be important for fluency during syllable-based metronome-paced speech for PWS. Future studies should continue examining the necessity of this reduction. In addition, speech rate must be controlled in future fluency-inducing condition studies, including neuroimaging investigations, in order for this research to make a substantial contribution to finding the fluency-inducing mechanism of fluency-inducing conditions.

Motor Learning Cannot Explain Stuttering Adaptation

When persons who stutter (PWS) read a text repeatedly, there is a progressive reduction in stutter frequency over the course of three to five readings. Recently, this phenomenon has been attributed by some researchers to motor learning-the acquisition of relatively permanent motor skills that facilitate fluency through practice in producing words. The current study tested this explanation. 23 PWS read prose passages five times in succession. The number of 'new' and 'old' stutters during repeated readings (words stuttered in the current reading but spoken fluently in the previous reading and words stuttered also in the previous reading) were analyzed. If motor learning facilitated fluency during repeated readings in PWS, words read fluently in a reading should not be stuttered in a later reading in significant numbers. Contrary to this prediction, there was no statistical difference in the number of new words stuttered across five readings. A plausible alternative explanation, which requires further study to verify, is offered.

Verbal Implicit Sequence Learning in Persons Who Stutter and Persons With Parkinson's Disease

ABSTRACTThe authors investigated the integrity of implicit learning systems in 14 persons with Parkinson's disease (PPD), 14 persons who stutter (PWS), and 14 control participants. In a 120-min session participants completed a verbal serial reaction time task, naming aloud 4 syllables in response to 4 visual stimuli. Unbeknownst to participants, the syllables formed a repeating 8-item sequence. PWS and PPD demonstrated slower reaction times for early but not late learning trials relative to controls reflecting delays but not deficiencies in general learning. PPD also demonstrated less accuracy in general learning relative to controls. All groups demonstrated similar limited explicit sequence knowledge. Both PWS and PPD demonstrated significantly less implicit sequence learning relative to controls, suggesting that stuttering may be associated with compromised functional integrity of the cortico-striato-thalamo-cortical loop.

Exploring auditory-motor interactions in normal and disordered speech

Auditory feedback plays an important role in speech motor learning and in the online correction of speech movements. Speakers can detect and correct auditory feedback errors at the segmental and suprasegmental levels during ongoing speech. The frontal brain regions that contribute to these corrective movements have also been shown to be more active during speech in persons who stutter (PWS) compared to fluent speakers. Further, various types of altered auditory feedback can temporarily improve the fluency of PWS, suggesting that atypical auditory-motor interactions during speech may contribute to stuttering disfluencies. To investigate this possibility, we have developed and improved Audapter, a software that enables configurable dynamic perturbation of the spatial and temporal content of the speech auditory signal in real time. Using Audapter, we have measured the compensatory responses of PWS to static and dynamic perturbations of the formant content of auditory feedback and compared these responses with those from matched fluent controls. Our findings indicate deficient utilization of auditory feedback by PWS for short-latency online control of the spatial and temporal parameters of articulation during vowel production and during running speech. These findings provide further evidence that stuttering is associated with aberrant auditory-motor integration during speech.

Investigating the neural basis of stuttering using transcranial magnetic stimulation: Preliminary case discussions

Neuroimaging studies have found particular areas of the brain to be over- or under-active in persons who stutter (PWS) suggestive of atypical lateralization of speech and language processing. This study used single pulse transcranial magnetic stimulation (TMS) to investigate differences in left and right tongue motor cortex excitability in three adult male PWS compared with five adult control speakers (four males). TMS pulses were applied to the left and right side of the head over the tongue motor cortices. Measures of excitability included: active motor threshold (AMT, i.e. the amount of stimulation required to elicit a consistent motor evoked potential (MEP) in the tongue), and the y-intercept and slope of linear regressions derived from plots of electromyography contraction levels versus MEP amplitudes (input–output facilitation curves). The results are presented as a series of case discussions. The control group exhibited increased excitability for the left tongue motor cortex compared with the right based on y-intercept measures, although no inter-hemispheric excitability differences were found based on AMT or slope measures. A reversed pattern of excitability was found for the PWS who exhibited decreased and increased left and right tongue motor cortex excitability, respectively, based on the y-intercept and AMT measures compared with the control group. The results provide support for the suggestion of inter-hemispheric excitability disturbances in PWS and warrants further investigation using TMS techniques.

Early-stage chunking of finger tapping sequences by persons who stutter and fluent speakers

This research note explored the hypothesis that chunking differences underlie the slow finger-tap sequencing performance reported in the literature for persons who stutter (PWS) relative to fluent speakers (PNS). Early-stage chunking was defined as an immediate and spontaneous tendency to organize a long sequence into pauses, for motor planning, and chunks of fluent motor performance. A previously published study in which 12 PWS and 12 matched PNS practised a 10-item finger tapping sequence 30 times was examined. Both groups significantly decreased the duration of between-chunk intervals (BCIs) and within-chunk intervals (WCIs) over practice. PNS had significantly shorter WCIs relative to PWS, but minimal differences between groups were found for the number of, or duration of, BCI. Results imply that sequencing differences found between PNS and PWS may be due to differences in automatizing movements within chunks or retrieving chunks from memory rather than chunking per se.

The effect of speech rate on stuttering frequency, phonated intervals, speech effort, and speech naturalness during chorus reading

PurposeThis study examined the effect of speech rate on phonated intervals (PIs), in order to test whether a reduction in the frequency of short PIs is an important part of the fluency-inducing mechanism of chorus reading. The influence of speech rate on stuttering frequency, speaker-judged speech effort, and listener-judged naturalness was also examined. An added purpose was to determine if chorus reading could be further refined so as to provide a perceptual guide for gauging the level of physical effort exerted during speech production. MethodsA repeated-measures design was used to compare data obtained during control reading conditions and during several chorus reading conditions produced at different speech rates. Participants included 8 persons who stutter (PWS) between the ages of 16 and 32years. ResultsThere were significant reductions in the frequency of short PIs from the habitual reading condition during slower chorus conditions, no change when speech rates were matched between habitual reading and chorus conditions, and an increase in the frequency of short PIs during chorus reading produced at a faster rate than the habitual condition. Speech rate did not have an effect on stuttering frequency during chorus reading. In general, speech effort ratings improved and naturalness ratings worsened as speech rate decreased. ConclusionThese results provide evidence that (a) a reduction in the frequency of short PIs is not necessary for fluency improvement during chorus reading, and (b) speech rate may be altered to provide PWS with a more appropriate reference for how physically effortful normally fluent speech production should be. Future investigations should examine the necessity of changes in the activation of neural regions during chorus reading, the possibility of defining individualized units on a 9-point effort scale, and if there are upper and lower speech rate boundaries for receiving ratings of “highly natural sounding” speech during chorus reading.Learning outcomes: The reader will be able to: (1) describe the effect of changes in speech rate on the frequency of short phonated intervals during chorus reading, (2) describe changes to speaker-judged speech effort as speech rate changes during chorus reading, (3) and describe the effect of changes in speech rate on listener-judged naturalness ratings during chorus reading.

Weak responses to auditory feedback perturbation during articulation in persons who stutter: evidence for abnormal auditory-motor transformation.

Previous empirical observations have led researchers to propose that auditory feedback (the auditory perception of self-produced sounds when speaking) functions abnormally in the speech motor systems of persons who stutter (PWS). Researchers have theorized that an important neural basis of stuttering is the aberrant integration of auditory information into incipient speech motor commands. Because of the circumstantial support for these hypotheses and the differences and contradictions between them, there is a need for carefully designed experiments that directly examine auditory-motor integration during speech production in PWS. In the current study, we used real-time manipulation of auditory feedback to directly investigate whether the speech motor system of PWS utilizes auditory feedback abnormally during articulation and to characterize potential deficits of this auditory-motor integration. Twenty-one PWS and 18 fluent control participants were recruited. Using a short-latency formant-perturbation system, we examined participants’ compensatory responses to unanticipated perturbation of auditory feedback of the first formant frequency during the production of the monophthong [ε]. The PWS showed compensatory responses that were qualitatively similar to the controls’ and had close-to-normal latencies (∼150 ms), but the magnitudes of their responses were substantially and significantly smaller than those of the control participants (by 47% on average, p<0.05). Measurements of auditory acuity indicate that the weaker-than-normal compensatory responses in PWS were not attributable to a deficit in low-level auditory processing. These findings are consistent with the hypothesis that stuttering is associated with functional defects in the inverse models responsible for the transformation from the domain of auditory targets and auditory error information into the domain of speech motor commands.