Comparison of performance of automatic recognizers for stutters in speech trained with event or interval markers.

Introduction: Automatic recognition of stutters (ARS) from speech recordings can facilitate objective assessment and intervention for people who stutter. However, the performance of ARS systems may depend on how the speech data are segmented and labelled for training and testing. This study compared two segmentation methods: event-based, which delimits speech segments by their fluency status, and interval-based, which uses fixed-length segments regardless of fluency. Methods: Machine learning models were trained and evaluated on interval-based and event-based stuttered speech corpora. The models used acoustic and linguistic features extracted from the speech signal and the transcriptions generated by a state-of-the-art automatic speech recognition system. Results: The results showed that event-based segmentation led to better ARS performance than interval-based segmentation, as measured by the area under the curve (AUC) of the receiver operating characteristic. The results suggest differences in the quality and quantity of the data because of segmentation method. The inclusion of linguistic features improved the detection of whole-word repetitions, but not other types of stutters. Discussion: The findings suggest that event-based segmentation is more suitable for ARS than interval-based segmentation, as it preserves the exact boundaries and types of stutters. The linguistic features provide useful information for separating supra-lexical disfluencies from fluent speech but may not capture the acoustic characteristics of stutters. Future work should explore more robust and diverse features, as well as larger and more representative datasets, for developing effective ARS systems.

Can listeners predict whether or not a stutter follows a stretch of fluent speech?

PURPOSE: Neurophysiological studies report that people who stutter (PWS) exhibit enhanced motor preparation before they stutter. This motor preparation pattern raises the possibility of detecting upcoming stutter moments before they actually occur. This study examined whether these motor preparation differences are detectable by listeners in the corresponding acoustic signal, thereby allowing them to predict upcoming stuttering moments. If so, features in these acoustic patterns could potentially be employed by computational procedures to automate detection of upcoming stutters and to target auditory feedback alterations specifically on these locations. METHODS: Forty healthy normal-hearing participants (aged 18-30) listened to seemingly fluent speech extracts each of which was either followed by a fluent (control condition) or stuttered (experimental condition) moment after the fluent extract. Participants listened to each extract and rated the likelihood of the speaker stuttering on the next word on a scale of 1 (very unlikely) to 7 (very likely) as to whether they thought there was a subsequent stutter. Several measures were made on the speech extracts which were examined either as control requirements to ensure no differences between experimental and control material or as covariates to assess any effects they had on judgments between the two conditions. RESULTS: Listeners gave significantly higher stutter-likelihood ratings for speech originally followed by a stuttered moment although effects were small. CONCLUSIONS: Naive listeners rated speech extracts that were subsequently followed by stuttered moments as more likely to be followed by a stutter than those that were followed by fluent words after the effects of significant covariates were excluded.

Factors affecting judgment accuracy when scoring children's responses to non-word repetition stimuli in real time.

BACKGROUND: Non-word repetition (NWR) tests are an important way speech and language therapists (SaLTs) assess language development. NWR tests are often scored whilst participants make their responses (i.e., in real time) in clinical and research reports (documented here via a secondary analysis of a published systematic review). AIMS: The main aim was to determine the extent to which real-time coding of NWR stimuli at the whole-item level (as correct/incorrect) was predicted by models that had varying levels of detail provided from phonemic transcriptions using several linear mixed method (LMM) models. METHODS & PROCEDURES: Live scores and recordings of responses on the universal non-word repetition (UNWR) test were available for 146 children aged between 3 and 6 years where the sample included all children starting in five UK schools in one year or two consecutive years. Transcriptions were made of responses to two-syllable NWR stimuli for all children and these were checked for reliability within and between transcribers. Signal detection analysis showed that consonants were missed when judgments were made live. Statistical comparisons of the discrepancies between target stimuli and transcriptions of children's responses were then made and these were regressed against live score accuracy. Six LMM models (three normalized: 1a, 2a, 3a; and three non-normalized: 1b, 2b, 3b) were examined to identify which model(s) best captured the data variance. Errors on consonants for live scores were determined by comparison with the transcriptions in the following ways (the dependent variables for each pair of models): (1) consonants alone; (2) substitutions, deletions and insertions of consonants identified after automatic alignment of live and transcribed materials; and (3) as with (2) but where substitutions were coded further as place, manner and voicing errors. OUTCOMES & RESULTS: The normalized model that coded consonants in non-words as 'incorrect' at the level of substitutions, deletions and insertions (2b) provided the best fit to the real-time coding responses in terms of marginal R2, Akaike's information criterion (AIC) and Bayesian information criterion (BIC) statistics. CONCLUSIONS & IMPLICATIONS: Errors that occur on consonants when non-word stimuli are scored in real time are characterized solely by the substitution, deletion and insertion measure. It is important to know that such errors arise when real-time judgments are made because NWR tasks are used to assess and diagnose several cognitive-linguistic impairments. One broader implication of the results is that future work could automate the analysis procedures to provide the required information objectively and quickly without having to transcribe data. WHAT THIS PAPER ADDS: What is already known on this subject Children and patients with a wide range of cognitive and language difficulties are less accurate relative to controls when they attempt to repeat non-words. Responses to non-words are often scored as correct or incorrect at the time the test is conducted. Limited assessments of this scoring procedure have been conducted to date. What this study adds to the existing knowledge Live NWR scores made by 146 children were available and the accuracy of these judgements was assessed here against ones based on phonemic transcriptions. Signal detection analyses showed that live scoring missed consonant errors in children's responses. Further analyses, using linear mixed effect models, showed that live judgments led to consonant substitution, deletion and insertion errors. What are the practical and clinical implications of this work? Improved and practicable NWR scoring procedures are required to provide SaLTs with better indications about children's language development (typical and atypical) and for clinical assessments of older people. The procedures currently used miss substitutions, deletions and insertions. Hence, procedures are required that provide the information currently only available when materials are transcribed manually. The possibility of training automatic speech recognizers to provide this level of detail is raised.

The possible role of early-stage phase-locked neural activities in speech-in-noise perception in human adults across age and hearing loss.

Ageing affects auditory neural phase-locked activities which could increase the challenges experienced during speech-in-noise (SiN) perception by older adults. However, evidence for how ageing affects SiN perception through these phase-locked activities is still lacking. It is also unclear whether influences of ageing on phase-locked activities in response to different acoustic properties have similar or different mechanisms to affect SiN perception. The present study addressed these issues by measuring early-stage phase-locked encoding of speech under quiet and noisy backgrounds (speech-shaped noise (SSN) and multi-talker babbles) in adults across a wide age range (19-75 years old). Participants passively listened to a repeated vowel whilst the frequency-following response (FFR) to fundamental frequency that has primary subcortical sources and cortical phase-locked response to slowly-fluctuating acoustic envelopes were recorded. We studied how these activities are affected by age and age-related hearing loss and how they are related to SiN performances (word recognition in sentences in noise). First, we found that the effects of age and hearing loss differ for the FFR and slow-envelope phase-locking. FFR was significantly decreased with age and high-frequency (≥ 2 kHz) hearing loss but increased with low-frequency (< 2 kHz) hearing loss, whilst the slow-envelope phase-locking was significantly increased with age and hearing loss across frequencies. Second, potential relationships between the types of phase-locked activities and SiN perception performances were also different. We found that the FFR and slow-envelope phase-locking positively corresponded to SiN performance under multi-talker babbles and SSN, respectively. Finally, we investigated how age and hearing loss affected SiN perception through phase-locked activities via mediation analyses. We showed that both types of activities significantly mediated the relation between age/hearing loss and SiN perception but in distinct manners. Specifically, FFR decreased with age and high-frequency hearing loss which in turn contributed to poorer SiN performance but increased with low-frequency hearing loss which in turn contributed to better SiN performance under multi-talker babbles. Slow-envelope phase-locking increased with age and hearing loss which in turn contributed to better SiN performance under both SSN and multi-talker babbles. Taken together, the present study provided evidence for distinct neural mechanisms of early-stage auditory phase-locked encoding of different acoustic properties through which ageing affects SiN perception.

Identifying Stuttering in Arabic Speakers Who Stutter: Development of a Non-word Repetition Task and Preliminary Results.

Stuttering and other conditions that affect speech fluency need to be identified at an early age in order that effective interventions can be given before the problems becomes chronic. This applies in countries where several languages are spoken including those in which English and Arabic are both widely used which calls for assessment procedures that work across these languages. The 'universal' non-word repetition task (UNWR) has been established as an effective screening tool for discriminating between children who stutter (CWS) and children with word-finding difficulty for a number of languages. However, the UNWR does not apply to languages such as Arabic and Spanish. The present study aimed to: (1) introduce an Arabic English NWR (AEN_NWR); which was developed based on the same phonologically informed approach used with UNWR; (2) present preliminary non-word repetition data from Arabic-speaking CWS and adults who stutter (AWS). The AEN_NWR items comprises twenty-seven non-words that meet lexical phonology constraints across Arabic and English. The set of items includes non-words of two, three and four syllables in length. Preliminary non-word repetition data were collected from ten CWS between the ages of 6;5 and 16;7 (M age = 12:1) and fourteen AWS between the ages of 19;2 and 31;0 (M age = 24). Participants performed the non-word repetition task and provided a sample of spontaneous speech. The spontaneous speech samples were used to estimate %stuttered syllables (%SS). To validate that AEN_NWR performance provides an alternative way of assessing stuttering, a significant correlation was predicted between %SS and AEN_NWR performance. Also, word length should affect repetition accuracy of AEN_NWR. As predicted, there was a significant negative correlation between the AEN_NWR and %SS scores (r (25) = -0.5), p < 0.000). Overall, CWS were less accurate in their repetition than AWS at all syllable lengths. The AEN_NWR provides a new assessment tool for detecting stuttering in speaker of Arabic and English. Future studies would benefit from a larger sample of participants, and by testing a population-based sample. These studies would allow further investigation of the AEN_NWR as a screening measure for stuttering in preschool children.

Causal Relationship between the Right Auditory Cortex and Speech-Evoked Envelope-Following Response: Evidence from Combined Transcranial Stimulation and Electroencephalography.

Speech-evoked envelope-following response (EFR) reflects brain encoding of speech periodicity that serves as a biomarker for pitch and speech perception and various auditory and language disorders. Although EFR is thought to originate from the subcortex, recent research illustrated a right-hemispheric cortical contribution to EFR. However, it is unclear whether this contribution is causal. This study aimed to establish this causality by combining transcranial direct current stimulation (tDCS) and measurement of EFR (pre- and post-tDCS) via scalp-recorded electroencephalography. We applied tDCS over the left and right auditory cortices in right-handed normal-hearing participants and examined whether altering cortical excitability via tDCS causes changes in EFR during monaural listening to speech syllables. We showed significant changes in EFR magnitude when tDCS was applied over the right auditory cortex compared with sham stimulation for the listening ear contralateral to the stimulation site. No such effect was found when tDCS was applied over the left auditory cortex. Crucially, we further observed a hemispheric laterality where aftereffect was significantly greater for tDCS applied over the right than the left auditory cortex in the contralateral ear condition. Our finding thus provides the first evidence that validates the causal relationship between the right auditory cortex and EFR.

Phonetic complexity and stuttering in Turkish-speaking children who stutter.

The relationship between stuttering and phonetic complexity for words spoken by Turkish children who stutter was investigated. The research questions were: (1) Do Turkish-speaking children stutter more on unbound content words than on unbound function words? (2) Do Turkish-speaking children stutter more on words with higher phonetic complexity scores? Twenty-one monolingual children aged 6-11 years who had a clinical diagnosis of stuttering participated. Speech samples were transcribed and lexical categories determined. Phonetic complexity was assessed by an adaptation of Index of Phonetic Complexity (IPC) for Turkish. Results revealed that the mean rank of unbound content words differed significantly from the mean rank of unbound function words and that stuttering frequency for unbound content words was significantly higher than for unbound function words.

Voice onset time and formant onset frequencies in Arabic stuttered speech.

Neuromuscular models of stuttering consider that making transitions between phones results in inappropriate temporal arrangements of articulators in people who stutter (PWS). Using this framework, the current study examined the acoustic productions of two fine-grained phonetic features: voice onset time (VOT) and second formant (F2). The hypotheses were that PWS should differ from fluent persons (FP) in VOT duration and F2 onset frequency as a result of the transition deficit for environments with complex phonetic features such as Arabic emphatics. Ten adolescent PWS and 10 adolescent FPs participated in the study. They read and memorized four monosyllabic plain-emphatic words silently. Data were analyzed by Repeated Measures ANOVAs. The positive and negative VOT durations of/t/vs./tˁ/and/d/vs./dˁ/and F2 onset frequency were measured acoustically. Results showed that stuttering was significantly affected by emphatic consonants. PWS had atypical VOT durations and F2 values. Findings are consistent with the atypicality of VOT and F2 reported for English-speaking PWS. This atypicality is realized differently in Arabic depending on the articulatory complexity and cognitive load of the sound.

Does Working-Memory Training Given to Reception-Class Children Improve the Speech of Children at Risk of Fluency Difficulty?

Procedures were designed to test for the effects of working-memory training on children at risk of fluency difficulty that apply to English and to many of the languages spoken by children with English as an Additional Language (EAL) in UK schools. Working-memory training should: (1) improve speech fluency in high-risk children; (2) enhance non-word repetition (NWR) (phonological) skills for all children; (3) not affect word-finding abilities. Children starting general education (N = 232) were screened to identify those at risk of fluency difficulty. Children were selected who were at high-risk (12), or low-risk (27) of fluency difficulty. For the low-risk children 10 received, and 17 did not receive, the working-memory training. All children in the treatment groups received working-memory training over a 2-week period. For the high-risk group, fluency improved and lasted for at least a week after the end of the study. Phonological skills improved in this group and in the low-risk group who received the training and the improvements continued for at least a week. The low-risk group who did not receive working-memory training showed no improvements, and no group improved word-finding ability.

Modulation of phase-locked neural responses to speech during different arousal states is age-dependent.

Phase-locked responses are vital for auditory perception and they may vary with participants' arousal state and age. Two phase-locked neural responses that reflect fine-grained acoustic properties of speech were examined in the current study: the frequency-following response (FFR) to the speech fundamental frequency (F0), which originates primarily from the auditory brainstem, and the theta-band phase-locked response (θ-PLV) to the speech envelope that originates from the auditory cortices. The ways these responses were affected by arousal in adults across a wide age-range (19-75 years) were examined. Extracts from electroencephalographic (EEG) responses to repeated syllables were classified into either high or low arousal state based on the occurrence of sleep spindles. The magnitudes of both FFRs and θ-PLVs were statistically greater in the high, than in the low, arousal state. The difference in θ-PLV between the two arousal states was significantly associated with sleep spindle density in the young, but not the older, adults. The results show that (1) arousal affects phase-locked processing of speech at cortical/sub-cortical sensory levels; and that (2) there is an interplay between aging and arousal state which indicates that sleep spindles have an age-dependent neuro-regulatory role on cortical processes. The results lay the grounds for studying how cognitive states affect early-stage neural activity in the auditory system across the lifespan.

We Have a Voice: Exploring Participants' Experiences of Stuttering Modification Therapy.

Purpose: Qualitative data were obtained from 8 people who stutter about their experiences and changes they perceived following attendance of an intensive group therapy intervention. Measures that related to reductions in stuttering, improved communicative confidence, and impacts on stuttering and quality of life were used to complement the qualitative data. Method: Eight participants attended a group stuttering modification course for adults who stutter. They reported their experiences of therapy and perceived changes in a focus group immediately after therapy and at a semistructured interview 6 months post-therapy. Participants completed 5 additional quantitative standardized outcome measures at 3 data collection points (before and directly after therapy and 6 months post-therapy). These measures provided information about stuttering severity and frequency, use of avoidance strategies, attitude change, communicative confidence, quality of life, and locus of control. Results: Thematic analysis of the qualitative data identified 4 main areas: thoughts, feelings, and behaviors before therapy and motivation for seeking therapy; direct experience of the course; learning outcomes and challenges and solutions for maintaining change; and ways in which attending therapy had made a difference. These reported changes were supported by the quantitative measures that demonstrated improved communicative confidence; increased self-awareness; affective, behavioral, and cognitive changes; reduced use of avoidance strategies; and lower impact of stuttering on quality of life. Conclusions: The qualitative analyses confirmed positive speech and attitude changes consequent on participants' attendance at stuttering modification therapy. These changes, further corroborated by quantitative measures, were linked to reports of improved quality of life. Further research is required to investigate the effectiveness of this form of therapy empirically and from the client's perspective.

Subtypes of stuttering determined by latent class analysis in two Swiss epidemiological surveys.

AIMS: Associations between stuttering in childhood and a broad spectrum of risk factors, associated factors and comorbidities were examined in two large epidemiological studies. Subtypes of stuttering were then identified based on latent class analysis (LCA). METHODS: Data were from two representative Swiss population samples: PsyCoLaus (N = 4,874, age 35-82 years) and the ZInEP Epidemiology Survey (N = 1,500, age 20-41 years). Associations between stuttering and sociodemographic characteristics, familial aggregation, comorbidity and psychosocial risk / associated factors were investigated in both samples. LCAs were conducted on selected items from people in both samples who reported having stuttered in childhood. RESULTS: Initial analyses linked early anxiety disorders, such as separation anxiety disorder and overanxious disorder, to stuttering (PsyCoLaus). ADHD was associated with stuttering in both datasets. In the analyses of risk / associated factors, dysfunctional parental relationships, inter-parental violence and further childhood adversities were mutual predictors of stuttering. Moreover, comorbidities were seen with hay fever, asthma, eczema and psoriasis (PsyCoLaus). Subsequent LCA identified an unspecific group of persons who self-reported that they stuttered and a group defined by associations with psychosocial adversities (ZINEP, PsyCoLaus) and atopic diseases (PsyCoLaus). CONCLUSIONS: The two subtypes of developmental stuttering have different risk / associated factors and comorbidity patterns. Most of the factors are associated with vulnerability mechanisms that occur early in life and that have also been linked with other neurodevelopmental disorders. Both psychosocial and biological factors appear to be involved in the etiopathogenesis of stuttering.

Identification of neural structures involved in stuttering using vibrotactile feedback.

Feedback delivered over auditory and vibratory afferent pathways has different effects on the fluency of people who stutter (PWS). These features were exploited to investigate the neural structures involved in stuttering. The speech signal vibrated locations on the body (vibrotactile feedback, VTF). Eleven PWS read passages under VTF and control (no-VTF) conditions. All combinations of vibration amplitude, synchronous or delayed VTF and vibrator position (hand, sternum or forehead) were presented. Control conditions were performed at the beginning, middle and end of test sessions. Stuttering rate, but not speaking rate, differed between the control and VTF conditions. Notably, speaking rate did not change between when VTF was delayed versus when it was synchronous in contrast with what happens with auditory feedback. This showed that cerebellar mechanisms, which are affected when auditory feedback is delayed, were not implicated in the fluency-enhancing effects of VTF, suggesting that there is a second fluency-enhancing mechanism.

Relationship between speech-evoked neural responses and perception of speech in noise in older adults.

Speech-in-noise (SPIN) perception involves neural encoding of temporal acoustic cues. Cues include temporal fine structure (TFS) and envelopes that modulate at syllable (Slow-rate ENV) and fundamental frequency (F0-rate ENV) rates. Here the relationship between speech-evoked neural responses to these cues and SPIN perception was investigated in older adults. Theta-band phase-locking values (PLVs) that reflect cortical sensitivity to Slow-rate ENV and peripheral/brainstem frequency-following responses phase-locked to F0-rate ENV (FFRENV_F0) and TFS (FFRTFS) were measured from scalp-electroencephalography responses to a repeated speech syllable in steady-state speech-shaped noise (SpN) and 16-speaker babble noise (BbN). The results showed that (1) SPIN performance and PLVs were significantly higher under SpN than BbN, implying differential cortical encoding may serve as the neural mechanism of SPIN performance that varies as a function of noise types; (2) PLVs and FFRTFS at resolved harmonics were significantly related to good SPIN performance, supporting the importance of phase-locked neural encoding of Slow-rate ENV and TFS of resolved harmonics during SPIN perception; (3) FFRENV_F0 was not associated to SPIN performance until audiometric threshold was controlled for, indicating that hearing loss should be carefully controlled when studying the role of neural encoding of F0-rate ENV. Implications are drawn with respect to fitting auditory prostheses.

Planum temporale asymmetry in people who stutter.

PURPOSE: Previous studies have reported that the planum temporale - a language-related structure that normally shows a leftward asymmetry - had reduced asymmetry in people who stutter (PWS) and reversed asymmetry in those with severe stuttering. These findings are consistent with the theory that altered language lateralization may be a cause or consequence of stuttering. Here, we re-examined these findings in a larger sample of PWS. METHODS: We evaluated planum temporale asymmetry in structural MRI scans obtained from 67 PWS and 63 age-matched controls using: 1) manual measurements of the surface area; 2) voxel-based morphometry to automatically calculate grey matter density. We examined the influences of gender, age, and stuttering severity on planum temporale asymmetry. RESULTS: The size of the planum temporale and its asymmetry were not different in PWS compared with Controls using either the manual or the automated method. Both groups showed a significant leftwards asymmetry on average (about one-third of PWS and Controls showed rightward asymmetry). Importantly, and contrary to previous reports, the degree of asymmetry was not related to stuttering severity. In the manual measurements, women who stutter had a tendency towards rightwards asymmetry but men who stutter showed the same degree of leftwards asymmetry as male Controls. In the automated measurements, Controls showed a significant increase in leftwards asymmetry with age but this relationship was not observed in PWS. CONCLUSIONS: We conclude that reduced planum temporale asymmetry is not a prominent feature of the brain in PWS and that the asymmetry is unrelated to stuttering severity.

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

This study investigated changes in brain function that occurred over a 7-day behavioral intervention for adults who stutter (AWS). Thirteen AWS received the intervention (AWS+), and 13 AWS did not receive the intervention (AWS-). There were 13 fluent controls (FC-). All participants were scanned before and after the intervention. Whole-brain analysis pre-intervention showed significant differences in task-related brain activation between AWS and FC- in the right inferior frontal cortex (IFC) and left middle temporal cortex, but there were no differences between the two AWS groups. Across the 7-day period of the intervention, AWS+ alone showed a significant increase of brain activation in the left ventral IFC/insula. There were no changes in brain function for the other two groups. Further analysis revealed that the change did not correlate with resting-state functional connectivity (RSFC) that AWS showed in the cerebellum (Lu et al., 2012). However, both changes in task-related brain function and RSFC correlated with changes in speech fluency level. Together, these findings suggest that functional reorganization in a brain region close to the left IFC that shows anomalous function in AWS, occurs after a short-term behavioral intervention for stuttering.

Identification of fluency and word-finding difficulty in samples of children with diverse language backgrounds.

BACKGROUND: Stuttering and word-finding difficulty (WFD) are two types of communication difficulty that occur frequently in children who learn English as an additional language (EAL), as well as those who only speak English. The two disorders require different, specific forms of intervention. Prior research has described the symptoms of each type of difficulty. This paper describes the development of a non-word repetition test (UNWR), applicable across languages, that was validated by comparing groups of children identified by their speech and language symptoms as having either stuttering or WFD. AIMS: To evaluate whether non-word repetition scores using the UNWR test distinguished between children who stutter and those who have a WFD, irrespective of the children's first language. METHODS & PROCEDURES: UNWR was administered to ninety-six 4-5-year-old children attending UK schools (20.83% of whom had EAL). The children's speech samples in English were assessed for symptoms of stuttering and WFD. UNWR scores were calculated. OUTCOMES & RESULTS: Regression models were fitted to establish whether language group (English only/EAL) and symptoms of (1) stuttering and (2) WFD predicted UNWR scores. Stuttering symptoms predicted UNWR, whereas WFD did not. These two findings suggest that UNWR scores dissociate stuttering from WFD. There were no differences between monolingual English-speakers and children who had EAL. CONCLUSIONS & IMPLICATIONS: UNWR scores distinguish between stuttering and WFD irrespective of language(s) spoken, allowing future evaluation of a range of languages in clinics or schools.

Is it necessary to assess fluent symptoms, duration of dysfluent events, and physical concomitants when identifying children who have speech difficulties?

Riley's (1994) Stuttering Severity Instrument (SSI) has three components: a symptom frequency measure (%SS), average duration of the three longest stutters, and a physical concomitant (PC) score. An assessment of whether it was necessary to use all of these when using SSI-3 to identify which children are at risk of speech difficulties was performed. Participants were 879 reception class children aged 4-6 years from UK schools. The distributions of the separate components of SSI-3 were examined. Departures from normality were noted for each component. The features seen in the distribution of the individual components were also apparent in the distribution of the overall scores (this was not normal and had multiple modes). These findings undermine the usefulness of the overall measure for identifying children at risk of speech difficulties. Prior work used a fixed SSI-3 threshold to identify at risk children. Classification of children as fluent or at risk based on this threshold was compared with classifications based on thresholds applied to the individual components. Classifications were comparable for %SS, but less satisfactory for duration and PC. These findings suggest that %SS performs similarly to the overall SSI-3 scores when used to identify at risk children. Procedures for identifying at risk children in schools need to be short and easy to administer. Thus, since there is no justification for including all components of SSI-3 and duration and physical concomitants are not sensitive measures of fluency, a procedure based on the frequency measure alone is appropriate for use in schools.

Relationship between Speech Production and Perception in People Who Stutter.

Speech production difficulties are apparent in people who stutter (PWS). PWS also have difficulties in speech perception compared to controls. It is unclear whether the speech perception difficulties in PWS are independent of, or related to, their speech production difficulties. To investigate this issue, functional MRI data were collected on 13 PWS and 13 controls whilst the participants performed a speech production task and a speech perception task. PWS performed poorer than controls in the perception task and the poorer performance was associated with a functional activity difference in the left anterior insula (part of the speech motor area) compared to controls. PWS also showed a functional activity difference in this and the surrounding area [left inferior frontal cortex (IFC)/anterior insula] in the production task compared to controls. Conjunction analysis showed that the functional activity differences between PWS and controls in the left IFC/anterior insula coincided across the perception and production tasks. Furthermore, Granger Causality Analysis on the resting-state fMRI data of the participants showed that the causal connection from the left IFC/anterior insula to an area in the left primary auditory cortex (Heschl's gyrus) differed significantly between PWS and controls. The strength of this connection correlated significantly with performance in the perception task. These results suggest that speech perception difficulties in PWS are associated with anomalous functional activity in the speech motor area, and the altered functional connectivity from this area to the auditory area plays a role in the speech perception difficulties of PWS.

Complete Genome Sequences of Four African Horse Sickness Virus Strains from a Commercial Tetravalent Live Attenuated Vaccine.

This is a report of the complete genome sequences of plaque-selected isolates of each of the four virus strains included in a South African commercial tetravalent African horse sickness attenuated live virus vaccine.