Obtaining consensus on core components of stuttering intervention for adults: An e-Delphi Survey with key stakeholders.

BACKGROUND: Evidence-based practice involves the synthesis of multiple forms of evidence to inform clinical decision-making and treatment evaluation. Practice- and patient-based evidence are two forms of evidence that are under-represented in the stuttering literature. The collection of such knowledge is essential to support the design and delivery of effective stuttering interventions for adults. AIMS: To build stakeholder consensus on the core components of intervention for adults who stutter, and to establish a guiding framework for the design and development of evidence-based interventions for adults who stutter. METHODS & PROCEDURES: Adults who stutter and speech and language therapists (SLTs) with experience in providing stuttering intervention participated in the three-round e-Delphi Survey focused on: (1) identifying key stuttering intervention components, including principles, practices, and structural and contextual elements; and (2) obtaining group consensus on stuttering intervention components. Statements were categorized using the International Classification of Functioning, Disability and Health (ICF) model adapted to the study of stuttering. OUTCOMES & RESULTS: A total of 48 individuals agreed to participate: 48/48 (100%) completed the Round 1 questionnaire, 40/48 (83%) responded to Round 2 and 36/40 (90%) participated in Round 3. Following content analysis of Round 1, 101 statements were developed, and consensus was achieved on 89 statements perceived as representing the core components of stuttering intervention for adults. Categorization of these statements reflected the key stuttering intervention components relating to personal reactions to stuttering, limitations in life participation and environmental factors. CONCLUSIONS & IMPLICATIONS: Consensus on the core components of stuttering intervention was reached through engagement with key stakeholders. The evidence-based framework presented highlights the range of key intervention components a clinician should consider when designing interventions for adults who stutter. WHAT THIS PAPER ADDS: What is already known on the subject Evidence-based practice endorses the synthesis of multiple knowledge forms including research, practice and patient evidence to support clinical decision-making and treatment evaluation. The stuttering literature is characterized by an over-representation of efficacy evidence, with significantly less practice and patient evidence to guide clinical practice. What this paper adds to existing knowledge This study adds valuable practice- and patient-based evidence for effective stuttering intervention components for adults who stutter. These relate to personal reactions to stuttering, limitations in life participation and environmental factors. What are the potential or actual clinical implications of this work? This research presents a stakeholder-informed framework for stuttering intervention to guide SLTs working with adults who stutter in designing evidence-based interventions. The framework supports the adoption of a person-centred approach to intervention to ensure each client's unique needs, preferences, values and desired outcomes are explored and integrated into therapy.

Influence of bilateral cochlear implants on vocal control.

Receiving a cochlear implant (CI) can improve fundamental frequency (F0) control for deaf individuals, resulting in increased vocal pitch control. However, it is unclear whether using bilateral CIs, which often result in mismatched pitch perception between ears, will counter this benefit. To investigate this, 23 bilateral CI users were asked to produce a sustained vocalization using one CI, the other CI, both CIs, or neither. Additionally, a set of eight normal hearing participants completed the sustained vocalization task as a control group. The results indicated that F0 control is worse with both CIs compared to using the ear that yields the lowest vocal variability. The results also indicated that there was a large range of F0 variability even for the relatively stable portion of the vocalization, spanning from 6 to 46 cents. These results suggest that bilateral CIs can detrimentally affect vocal control.

Suppression of vocal responses to auditory perturbation with real-time visual feedback.

Speakers can adjust pitch using auditory feedback through a short-latency corrective response known as the pitch-shift response (PSR). Suppression of the PSR denotes on-line stabilization of pitch. In this paper, the hypothesis that pitch-shift responses can be suppressed with real-time visual feedback of vocal F0 is investigated. Mandarin speakers and naive speakers without tonal language experience were instructed to produce the sustained vowel /a/ and Mandarin tone /ma1/ in an audio-only condition and a separate audio-visual condition. Both Mandarin speakers and naive speakers suppressed pitch-shift responses in the audio-visual condition, regardless of task (/a/ or /ma1/) and stimulus magnitude (25 cents or 200 cents). These findings suggest that multisensory feedback (audio-visual) can improve the stability of voice F0. The benefit of audio-visual integration is independent of language experience.

Audio-vocal responses elicited in adult cochlear implant users.

Auditory deprivation experienced prior to receiving a cochlear implant could compromise neural connections that allow for modulation of vocalization using auditory feedback. In this report, pitch-shift stimuli were presented to adult cochlear implant users to test whether compensatory motor changes in vocal F0 could be elicited. In five of six participants, rapid adjustments in vocal F0 were detected following the stimuli, which resemble the cortically mediated pitch-shift responses observed in typical hearing individuals. These findings suggest that cochlear implants can convey vocal F0 shifts to the auditory pathway that might benefit audio-vocal monitoring.

Investigating Age-related changes in fine motor control across different effectors and the impact of white matter integrity.

Changes in fine motor control that eventually compromise dexterity accompany advanced age; however there is evidence that age-related decline in motor control may not be uniform across effectors. Particularly, the role of central mechanisms in effector-specific decline has not been examined but is relevant for placing age-related motor declines into the growing literature of age-related changes in brain function. We examined sub-maximal force control across three different effectors (fingers, lips, and tongue) in 18 young and 14 older adults. In parallel with the force variability measures we examined changes in white matter structural integrity in effector-specific pathways in the brain with diffusion tensor imaging (DTI). Motor pathways for each effector were identified by using an fMRI localizer task followed by tractography to identify the fiber tracts propagating to the midbrain. Increases in force control variability were found with age in all three effectors but the effectors showed different degrees of age-related variability. Motor control changes were accompanied by a decline in white matter structural integrity with age shown by measures of fractional anisotropy and radial diffusivity. The DTI metrics appear to mediate some of the age-related declines in motor control. Our findings indicate that the structural integrity of descending motor systems may play a significant role in age-related increases in motor performance variability, but that differential age-related declines in oral and manual effectors are not likely due to structural integrity of descending motor pathways in the brain.

Transcranial direct current stimulation over the right dorsolateral prefrontal cortex increases oxyhemoglobin concentration and cognitive performance dependent on cognitive load.

Transcranial direct current stimulation (tDCS) has been explored as a potential method for cognitive enhancement. tDCS may induce a cascade of neurophysiological changes including alterations in cerebral oxygenation. However, the effects of tDCS on the cognitive-cerebral oxygenation interaction remains unclear. Further, oxygenation variability across individuals remains minimally controlled for. The purpose of this sham-controlled study was to test the effects of anodal tDCS over the right dorsolateral prefrontal cortex (DLPFC) on the interaction between working memory and cerebral oxygenation while controlling for individual oxygenation variability. Thirty-three adults received resting-state functional near-infrared spectroscopy (fNIRS) recordings over bilateral prefrontal cortices. Following this, working memory was tested using a Toulouse n-back task concurrently paired with fNIRS, with measurements taken before and after 20 min of anodal or sham tDCS at 1.5 mA. With individual oxygenation controlled for, anodal tDCS was found to increase the oxyhemoglobin concentration over the right DLPFC during the 2-back (q = .015) and 3-back (q = .008) conditions. Additionally, anodal tDCS was found to improve accuracy during the 3-back task by 13.4 % (p = .028) and decrease latency by 250 ms (p = .013). The increase in oxyhemoglobin was strongly correlated with increases in accuracy (p = .041) and decreases in latency during the 3-back span (p = .017). Taken together, anodal tDCS over the right DLPFC was found to regionally increase oxyhemoglobin concentrations and improve working memory performance in higher cognitive load conditions.

It's Mine, . . . It's Mine: Unsolicited Repetitions Are Reduced in Toddlers.

A phenomenon called "repetition reduction" can increase articulation rate in adults by facilitating phonetic and motor processes, which indicates flexibility in the control of articulation rate. Young children, who speak much slower, may not have the same speech motor flexibility resulting in the absence of the repetition reduction effect. In this study, we tested whether spontaneous repetitions of young children are produced with a faster articulation rate than their original utterances. Twelve monolingual English-speaking children were observed at four time points between 2;0 and 3;0 years of age. A significant increase in articulation rate and syllable count was found using multilevel models for all utterances over the 1-year period. At each time point, however, the repeated utterances were produced significantly faster than the original utterances even though the content and syllable count differed minimally. Our findings conform to the pattern of adult studies suggesting that a "naturistic" form of repetition reduction is already present in the speech of children at 2;0 years. Although certain aspects of speech motor control are undergoing rapid development, existing motor capability at 2;0 already supports flexible changes in articulation rate including repetition reduction.

Oral sensorimotor integration in adults who stutter.

OBJECTIVE: To investigate the relationship between tendon vibration sensitivity and oral motor control in adults who stutter (AWS). PATIENTS AND METHODS: Ten controls and 10 AWS first made jaw-opening movements from a closed-mouth position to an 18-mm target. Then, masseter tendon vibration was applied during jaw opening in a separate condition to test whether accuracy and/or variability is related to movement undershoot. RESULTS: AWS made less accurate and more variable jaw movements than controls without visual feedback. Among the normally fluent adult participants, higher accuracy and lower variability were significantly related to masseter vibration undershoot, but significant correlations were not observed for AWS. CONCLUSION: These results suggest that increased tendon vibration sensitivity may be related to more refined oral motor control. Subtle sensorimotor limitations could be present in stuttering that render speech more susceptible to breakdowns.

Force control under auditory feedback: effector differences and audiomotor memory.

Audiomotor integration is a basic form of sensorimotor control for regulating vocal pitch and vocal loudness, but its contribution to general motor control has only been studied minimally. In this paper, auditory feedback for prolonged force control was investigated by comparing manual and oral force generation and testing short-term audiomotor memory for these effectors. Ten healthy volunteers between the ages of 20 and 30 years old were recruited. The participants produced continuous force for 30 sec. with the lip or finger to match auditory targets. In the feedback condition, when auditory feedback was provided for 30 sec., lip force was more variable than finger force. In the memory condition, the force output of both effectors remained stable for approximately 4 sec. after feedback removal, followed by significant decay. A longer short-term memory capacity could facilitate encoding of motor memories for tasks having acoustic goals. The results demonstrate that "audiomotor" integration was effective for sustaining forces, and that audiomotor force memory is comparable to reports of visuomotor force memory.

Speech kinematic variability in adults who stutter is influenced by treatment and speaking style.

AIM: We tested whether completion of the Comprehensive Stuttering Program (CSP) is associated with a reduction in speech kinematic variability relative to pre-treatment when adults who stutter (AWS) use a casual speaking manner or fluency skills. RATIONAL: Kinematic variability is higher in AWS suggesting a sensorimotor vulnerability; however, it is not clear whether high variability is a trait related to the underlying disorder or reflects the mutable state of stuttering. Speech restructuring intervention such as the CSP could support more consistent articulatory control and stable movement patterns. METHODOLOGY: Thirteen AWS were tested before and after completing the CSP while 11 adults who do not stutter (AWNS) completed a single session. Participants were instructed to use a casual manner of speaking in the first post-treatment session. In the second post-treatment condition, the AWS employed their fluency skills at a control speaking rate. An optical tracking system captured lower lip movements while participants spoke two English phrases and a complex nonword. Across-utterance kinematic variability was measured using the spatiotemporal index (STI) and within-utterance variability was measured with recurrence quantification analysis (RQA). RESULTS: There was a positive treatment outcome based on significant reductions in percentage syllables stuttered (%SS) during speaking and reading, decreases in stuttering severity and improved perceptions of stuttering and communication confidence. The STI of the AWS decreased significantly after treatment for both speaking styles. The RQA variables indicated that AWS used a less stereotyped and more flexible manner of speaking in the casual condition after treatment, but speech movement regularity increased when using fluency skills. CONCLUSIONS: The AWS showed a significant decrease in labial kinematic variability alongside a successful treatment outcome involving speech restructuring and cognitive behavioral techniques. These changes in across-utterance and within-utterance kinematic indices demonstrate that effective stuttering treatment can promote speech motor stability along with fluent speech.

Deficit or Difference? Effects of Altered Auditory Feedback on Speech Fluency and Kinematic Variability in Adults Who Stutter.

Purpose The purpose of this study was to test whether adults who stutter (AWS) display a different range of sensitivity to delayed auditory feedback (DAF). Two experiments were conducted to assess the fluency of AWS under long-latency DAF and to test the effect of short-latency DAF on speech kinematic variability in AWS. Method In Experiment 1, 15 AWS performed a conversational speaking task under nonaltered auditory feedback and 250-ms DAF. The rates of stuttering-like disfluencies, other disfluencies, and speech errors and articulation rate were compared. In Experiment 2, 13 AWS and 15 adults who do not stutter (AWNS) read three utterances under four auditory feedback conditions: nonaltered auditory feedback, amplified auditory feedback, 25-ms DAF, and 50-ms DAF. Across-utterance kinematic variability (spatiotemporal index) and within-utterance variability (percent determinism and stability) were compared between groups. Results In Experiment 1, under 250-ms DAF, the rate of stuttering-like disfluencies and speech errors increased significantly, while articulation rate decreased significantly in AWS. In Experiment 2, AWS exhibited higher kinematic variability than AWNS across the feedback conditions. Under 25-ms DAF, the spatiotemporal index of AWS decreased significantly compared to the other feedback conditions. AWS showed lower overall percent determinism than AWNS, but their percent determinism increased under 50-ms DAF to approximate that of AWNS. Conclusions Auditory feedback manipulations can alter speech fluency and kinematic variability in AWS. Longer latency auditory feedback delays induce speech disruptions, while subtle auditory feedback manipulations potentially benefit speech motor control. Both AWS and AWNS are susceptible to auditory feedback during speech production, but AWS appear to exhibit a distinct continuum of sensitivity.

Coordinating voicing onset with articulation: a potential role for sensory cues in shaping phonological distinctions.

In the typical speech of any language, voicing onset and offset are effortlessly coordinated with articulation as part of the intrinsic coordination of sound production. In this paper, we argue that voicing-articulatory coordination patterns could be shaped by sensory feedback during early speech learning and these patterns persist in mature syllable productions. Our experimental results show that voicing onset is closely associated with the peak velocity and peak amplitude of jaw and upper lip movements for VC syllables in adults. This robust coordination in the onset position may function to increase the salience of VC syllables and provide a phonetically natural explanation for vowels to undergo phonological lengthening and to avoid phonological reduction in word-initial onset position.

Masking auditory feedback does not eliminate repetition reduction.

Repetition reduces word duration. Explanations of this process have appealed to audience design, internal production mechanisms, and combinations thereof (e.g. Kahn & Arnold, 2015). Jacobs, Yiu, Watson, and Dell (2015) proposed the auditory feedback hypothesis, which states that speakers must hear a word, produced either by themselves or another speaker, in order for duration reduction on a subsequent production. We conducted a strong test of the auditory feedback hypothesis in two experiments, in which we used masked auditory feedback and whispering to prevent speakers from hearing themselves fully. Both experiments showed that despite limiting the sources of normal auditory feedback, repetition reduction was observed to equal extents in masked and unmasked conditions, suggesting that repetition reduction may be supported by multiple sources, such as somatosensory feedback and feedforward signals, depending on their availability.

Brain activation abnormalities during speech and non-speech in stuttering speakers.

Although stuttering is regarded as a speech-specific disorder, there is a growing body of evidence suggesting that subtle abnormalities in the motor planning and execution of non-speech gestures exist in stuttering individuals. We hypothesized that people who stutter (PWS) would differ from fluent controls in their neural responses during motor planning and execution of both speech and non-speech gestures that had auditory targets. Using fMRI with sparse sampling, separate BOLD responses were measured for perception, planning, and fluent production of speech and non-speech vocal tract gestures. During both speech and non-speech perception and planning, PWS had less activation in the frontal and temporoparietal regions relative to controls. During speech and non-speech production, PWS had less activation than the controls in the left superior temporal gyrus (STG) and the left pre-motor areas (BA 6) but greater activation in the right STG, bilateral Heschl's gyrus (HG), insula, putamen, and precentral motor regions (BA 4). Differences in brain activation patterns between PWS and controls were greatest in females and less apparent in males. In conclusion, similar differences in PWS from the controls were found during speech and non-speech; during perception and planning they had reduced activation while during production they had increased activity in the auditory area on the right and decreased activation in the left sensorimotor regions. These results demonstrated that neural activation differences in PWS are not speech-specific.

Common neural substrates support speech and non-speech vocal tract gestures.

The issue of whether speech is supported by the same neural substrates as non-speech vocal tract gestures has been contentious. In this fMRI study we tested whether producing non-speech vocal tract gestures in humans shares the same functional neuroanatomy as non-sense speech syllables. Production of non-speech vocal tract gestures, devoid of phonological content but similar to speech in that they had familiar acoustic and somatosensory targets, was compared to the production of speech syllables without meaning. Brain activation related to overt production was captured with BOLD fMRI using a sparse sampling design for both conditions. Speech and non-speech were compared using voxel-wise whole brain analyses, and ROI analyses focused on frontal and temporoparietal structures previously reported to support speech production. Results showed substantial activation overlap between speech and non-speech function in regions. Although non-speech gesture production showed greater extent and amplitude of activation in the regions examined, both speech and non-speech showed comparable left laterality in activation for both target perception and production. These findings posit a more general role of the previously proposed "auditory dorsal stream" in the left hemisphere--to support the production of vocal tract gestures that are not limited to speech processing.

Early Speech Rate Development: A Longitudinal Study.

Purpose Our knowledge of speech rate development remains inadequate because of limited longitudinal data and lack of data from children under age 3;0 (years;months). The purpose of this longitudinal study was to test the pattern of speech rate development between ages 2;0 and 3;0. Method Speech rate was assessed at 4 time points between ages 2;0 and 3;0. The analysis employed multilevel models to characterize the development of speech rate (syllables per second), phonemes per second (PPS), length of active declarative sentences, and mean length of utterance. Results The results indicate a significant linear increase in speech rate, PPS, length of active declarative sentences, and mean length of utterance occurring over the 1-year period. Male and female children differed in speech rate, PPS, and utterance length, suggesting sex is a potential factor in early speech rate development. Conclusions Our findings indicate that the speech motor system develops rapidly during the period when grammar emerges. Speech rate has the potential to be an important metric for understanding typical speech development and speech disorders.

Delayed Phonological Encoding in Stuttering: Evidence from Eye Tracking.

Stuttering is a multifactorial disorder that is characterized by disruptions in the forward flow of speech believed to be caused by differences in the motor and linguistic systems. Several psycholinguistic theories of stuttering suggest that delayed or disrupted phonological encoding contributes to stuttered speech. However, phonological encoding remains difficult to measure without controlling for the involvement of the speech-motor system. Eye-tracking is proposed to be a reliable approach for measuring phonological encoding duration while controlling for the influence of speech production. Eighteen adults who stutter and 18 adults who do not stutter read nonwords under silent and overt conditions. Eye-tracking was used to measure dwell time, number of fixations, and response time. Adults who stutter demonstrated significantly more fixations and longer dwell times during overt reading than adults who do not stutter. In the silent condition, the adults who stutter produced more fixations on the nonwords than adults who do not stutter, but dwell-time differences were not found. Overt production may have resulted in additional requirements at the phonological and phonetic levels of encoding for adults who stutter. Direct measurement of eye-gaze fixation and dwell time suggests that adults who stutter require additional processing that could potentially delay or interfere with phonological-to-motor encoding.

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.

Jaw-phonatory coordination in chronic developmental stuttering.

UNLABELLED: A deficiency in sensorimotor integration in a person who stutters may be a factor in the pathophysiology of developmental stuttering. To test oral sensorimotor function in adults who stutter, we used a task that requires the coordination of a jaw-opening movement with phonation onset. The task was adapted from previous limb coordination studies, which show that movement coordination depends on intact proprioception. We hypothesized that adult stutterers would show deficient jaw-phonatory coordination relative to control participants. The task required initiation of phonation as a jaw-opening movement passed through a narrow spatial target. Target amplitude and jaw movement speed were varied. The stuttering group showed significantly higher movement error and spatial variability in jaw-phonatory coordination compared to the control group, but group differences in movement velocity or duration were not found. The aberrant jaw-phonatory coordination of the stuttering participants suggests that stuttering is associated with an oral proprioceptive limitation, although, the findings are also consistent with a motor control deficit. LEARNING OUTCOMES: As a result of this activity, reader will (1) learn about a hypothesis and evidence supporting the view that a sensorimotor deficit contributes to chronic developmental stuttering and (2) will obtain information about the role of proprioception in multi-articulatory coordination and how it can be tested using an oral-phonatory coordination task.

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.