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.

Relation of motor, linguistic and temperament factors in epidemiologic subtypes of persistent and recovered stuttering: Initial findings.

PURPOSE: The purpose of this study was to determine the presence of any patterns reflecting underlying subtypes of persistence and recovery across epidemiologic, motor, language, and temperament domains in the same group of children beginning to stutter and followed for several years. METHODS: Participants were 58 2-4-year-old CWS and 40 age and gender matched NFC from four different sites in the Midwest. At the end of the multi-year study, stuttering children were classified as Persistent or Recovered. The same protocol obtaining data to measure stuttering, motor, language and temperament characteristics was used at each site. They have not been included in previous reports. RESULTS: The Persistent group performed consistently differently from the Recovered and Control groups. They performed lower on standardized language tests and in phonological accuracy, had greater kinematic variability, and were judged by their parents to be more negative in temperament. CONCLUSIONS: The present study provides data supporting the hypothesis that subtypes of stuttering can be identified along persistency/recovery lines, but results were not definitive. EDUCATIONAL OBJECTIVES: Readers will be able to (a) describe the current state of subtypes of stuttering research; (b) summarize possible contributions of epidemiologic, motoric, linguistic and temperament to such subtyping with regard to persistency and recovery.

Breastfeeding may protect against persistent stuttering.

PURPOSE: This study investigated the hypothesis that breastfeeding in infancy might protect against persistent stuttering in children. METHOD: We collected new data from the mothers of current and past participants in the Illinois Stuttering Research Program on their children's feeding history during infancy. We obtained 47 usable responses, for 17 children with persistent stuttering and 30 children who recovered naturally after a period of stuttering. RESULTS: A chi-squared test for linear trend revealed a significant relationship between breastfeeding duration and the likelihood of natural recovery for the boys in the sample. Mothers of children in the persistent group were no more likely to report early feeding difficulties which might have suggested an underlying oral motor deficit in children predisposed toward persistent stuttering. CONCLUSIONS: Our results offer preliminary support for the idea that breastfeeding may confer a measure of protection against persistent stuttering. The fatty acid profile of human milk, with its potential to affect both gene expression and the composition of neural tissue, may explain this association. Further research is called for. LEARNING OUTCOMES: The reader will be able to discuss at least one reason why human milk may make a difference in neurodevelopment generally and with regard to stuttering outcomes specifically. Additionally, the reader will be able to describe the relationship between breastfeeding duration and stuttering recovery observed in this sample.

Individual variability in delayed auditory feedback effects on speech fluency and rate in normally fluent adults.

PURPOSE: Delayed auditory feedback (DAF) is known to induce stuttering-like disfluencies (SLDs) and cause speech rate reductions in normally fluent adults, but the reason for speech disruptions is not fully known, and individual variation has not been well characterized. Studying individual variation in susceptibility to DAF may identify factors that predispose an individual to be more or less dependent on auditory feedback. METHOD: Participants were 62 normally fluent adults. Each participant performed a spontaneous speech task in 250-ms DAF and amplified nondelayed auditory feedback (NAF) conditions. SLDs, other disfluencies (ODs), speech errors (SEs), and articulation rate (AR) were measured under each condition. RESULTS: In the DAF condition, SLDs and SEs significantly increased, and AR decreased. Sex had a limited effect in that men exhibited higher rates of ODs and faster AR than women. More important, parametric cluster analysis identified that 2- and 3-subgroup solutions reveal important variation that differentiates tendencies toward disfluency changes and rate reduction under DAF, which are theoretically and empirically preferred to a single-group solution. CONCLUSION: Individual variability in response to DAF may be accounted for by subgroups of individuals. This suggests that certain normally fluent individuals could be more dependent on intact feedback to maintain fluency.

Differences of articulation rate and utterance length in fluent and disfluent utterances of preschool children who stutter.

PURPOSE: The purpose of this study was to investigate characteristics of four types of utterances in preschool children who stutter: perceptually fluent, containing normal disfluencies (OD utterance), containing stuttering-like disfluencies (SLD utterance), and containing both normal and stuttering-like disfluencies (SLD+OD utterance). Articulation rate and length of utterance were measured to seek the differences. Because articulation rate may reflect temporal aspects of speech motor control, it was predicted that the articulation rate would be different between perceptually fluent utterances and utterances containing disfluencies. The length of utterance was also expected to show different patterns. METHOD: Participants were 14 preschool children who stutter. Disfluencies were identified from their spontaneous speech samples, and articulation rate in syllables per second and utterance length in syllables were measured for the four types of utterances. RESULTS AND DISCUSSION: There was no significant difference in articulation rate between each type of utterance. Significantly longer utterances were found only in SLD+OD utterances compared to fluent utterances, suggesting that utterance length may be related to efforts in executing motor as well as linguistic planning. The SLD utterance revealed a significant negative correlation in that longer utterances tended to be slower in articulation rates. Longer utterances may place more demand on speech motor control due to more linguistic and/or grammatical features, resulting in stuttering-like disfluencies and a decreased rate.

Corpus callosum morphology in children who stutter.

UNLABELLED: Multiple studies have reported both functional and neuroanatomical differences between adults who stutter and their normally fluent peers. However, the reasons for these differences remain unclear although some developmental data suggest that structural brain differences may be present in school-age children who stutter. In the present study, the corpus callosum of children with persistent stuttering, children who recovered from stuttering and typically developing children between 9 and 12 years of age was compared to test if the presence of aberrant callosal morphology is implicated in this disorder. The total corpus callosum midsagittal area and area of each subsection consisting of the rostrum, anterior midbody, posterior midbody and splenium were measured using MIPAV (Medical Image Processing, Analysis, and Visualization). Voxel-based morphometry (VBM) was also used to compare white matter volume. No differences were detected in the corpus callosum area or white matter volume between children with persistent stuttering, children who recovered from stuttering and typically developing children. These results agree with dichotic listening studies that indicate children who stutter show the typical right ear advantage. Therefore, the neural reorganization across the midline shown in adults who stutter may be the result of long-term adaptations to persistent stuttering. EDUCATIONAL OBJECTIVES: After reading this article, the reader will be able to: (1) summarize research findings on corpus callosum development; and (2) discuss the characteristics of corpus callosum anatomy in stuttering.

Developing physiologic stress profiles for school-age children who stutter.

PURPOSE: Physiologic reactivity profiles were generated for 9 school-age children with a history of stuttering. Utilizing salivary sampling, stress biomarkers cortisol and alpha-amylase were measured in response to normal daily stressors. Children with a history of stuttering were characterized as high or low autonomic reactors when compared to age-normed references established for cortisol and alpha-amylase levels. METHOD: Salivary samples were collected four times daily over three consecutive days from children (6 boys and 3 girls) aged 6-11 years. Samples were measured for two important stress biomarkers, cortisol and alpha-amylase. Following laboratory training on appropriate sampling technique using the Salivette, families collected all samples in their homes. RESULTS: Compared to published references established for normal children, children with a history of stuttering exhibited mean cortisol and alpha-amylase levels that were significantly lower, though within normal limits. CONCLUSIONS: Results reflect an initial investigation into the use of salivary sampling to measure reactivity in children who stutter. As children who stutter have historically been excluded from physiologic stress studies, salivary sampling appears to provide an innovative and minimally invasive option for investigators. Though interpreted with caution secondary to the small sample size, initial findings suggest that in response to normal daily stressors, school-age children with a history of stuttering do not exhibit significantly elevated stress biomarkers. EDUCATIONAL OBJECTIVES: The reader will be able to: (1) identify two biomarkers that reflect activation of the body's stress response; (2) discuss possible implications the generation of individualized stress profiles may have on the treatment of stuttering; and (3) discuss and evaluate the research needs associated with the inclusion of children in physiological studies of fluency.

Functional brain activation differences in stuttering identified with a rapid fMRI sequence.

UNLABELLED: The purpose of this study was to investigate whether brain activity related to the presence of stuttering can be identified with rapid functional MRI (fMRI) sequences that involved overt and covert speech processing tasks. The long-term goal is to develop sensitive fMRI approaches with developmentally appropriate tasks to identify deviant speech motor and auditory brain activity in children who stutter closer to the age at which recovery from stuttering is documented. Rapid sequences may be preferred for individuals or populations who do not tolerate long scanning sessions. In this report, we document the application of a picture naming and phoneme monitoring task in 3 min fMRI sequences with adults who stutter (AWS). If relevant brain differences are found in AWS with these approaches that conform to previous reports, then these approaches can be extended to younger populations. Pairwise contrasts of brain BOLD activity between AWS and normally fluent adults indicated the AWS showed higher BOLD activity in the right inferior frontal gyrus (IFG), right temporal lobe and sensorimotor cortices during picture naming and higher activity in the right IFG during phoneme monitoring. The right lateralized pattern of BOLD activity together with higher activity in sensorimotor cortices is consistent with previous reports, which indicates rapid fMRI sequences can be considered for investigating stuttering in younger participants. EDUCATIONAL OBJECTIVES: The reader will learn about and be able to describe the: (1) use of functional MRI to study persistent developmental stuttering; (2) differences in brain activation between persons who stutter and normally fluent speakers; and (3) potential benefit of time efficient fMRI sequences combined with a range of speech processing tasks for investigating stuttering in younger populations.

Corpus callosum differences associated with persistent stuttering in adults.

Recent studies have implicated anatomical differences in speech-relevant brain regions of adults who stutter (AWS) compared to normally fluent adults (NFA). The present study focused on the region of the corpus callosum (CC) which is involved in interhemispheric processing between the left and right cerebral hemispheres. Two-dimensional segmentation of area and voxel-based morphometry were used to evaluate the corpus callosum. Results revealed that the rostrum and anterior midbody of the CC were larger in AWS than NFA. In addition, the overall callosa area was larger in AWS than NFA. The group comparison of white matter volume showed a cluster of increased white matter volume predominantly encompassing the rostrum across the midline portion in AWS. These results potentially reflect anatomical changes associated with differences in the hemispheric distribution of language processes that have been reported previously in AWS.

Influences of rate, length, and complexity on speech disfluency in a single-speech sample in preschool children who stutter.

UNLABELLED: The purpose of the present study was (1) to determine whether speech rate, utterance length, and grammatical complexity (number of clauses and clausal constituents per utterance) influenced stuttering-like disfluencies as children became more disfluent at the end of a 1200-syllable speech sample [Sawyer, J., & Yairi, E. (2006). The effect of sample size on the assessment of stuttering severity. American Journal of Speech-Language Pathology, 15, 36-44] and (2) to explore the interaction of speech rate, length, and grammatical complexity at the beginning (syllables 1-300, Section A) and the end (syllables 901-1200, Section B) of the speech sample. Participants were eight boys and six girls (M=40.9 months) who were selected from the Sawyer and Yairi [Sawyer, J., & Yairi, E. (2006). The effect of sample size on the assessment of stuttering severity. American Journal of Speech-Language Pathology, 15, 36-44] study. Mean length of utterance (MLU) in morphemes, the number of clauses, clausal constituents, and articulation rate, measured in syllables per second were analyzed from the children's conversational speech. The median split procedure [Logan, K., & Conture, E. (1995). Length, grammatical complexity, and rate differences in stuttered and fluent conversational utterances of children who stutter. Journal of Fluency Disorders, 20, 35-61; Yaruss, J. S. (1997). Utterance timing and childhood stuttering. Journal of Fluency Disorders, 22, 263-286] was used to study interactions between articulation rate, utterance length, and grammatical complexity across the two sections. The mean number of clauses per utterance, clausal constituents per utterance, and articulation rate revealed no significant differences between Section A and Section B, whereas MLU significantly increased in Section B (p=.013). Clausal constituents and MLU were significantly correlated both in Sections A and B. The median split procedure revealed trends for utterances characterized as high length and low-speech rate to be greater in number in Section B than A, but the differences were not significant. EDUCATIONAL OBJECTIVES: The reader will learn about and be able to: (a) describe the influence of grammatical complexity and mean length of utterance on disfluent speech; (b) compare different procedures for assessing speech rate and determine why the effects of articulation rate have been inconclusive; (c) discuss procedures for comparing length, rate, and complexity across a single-speech sample; and (d) explain why therapeutic methods that emphasize shorter utterance lengths, rather than only slower speech rates, are advisable in establishing fluency in preschool children who stutter.

Brain anatomy differences in childhood stuttering.

Stuttering is a developmental speech disorder that occurs in 5% of children with spontaneous remission in approximately 70% of cases. Previous imaging studies in adults with persistent stuttering found left white matter deficiencies and reversed right-left asymmetries compared to fluent controls. We hypothesized that similar differences might be present indicating brain development differences in children at risk of stuttering. Optimized voxel-based morphometry compared gray matter volume (GMV) and diffusion tensor imaging measured fractional anisotropy (FA) in white matter tracts in 3 groups: children with persistent stuttering, children recovered from stuttering, and fluent peers. Both the persistent stuttering and recovered groups had reduced GMV from normal in speech-relevant regions: the left inferior frontal gyrus and bilateral temporal regions. Reduced FA was found in the left white matter tracts underlying the motor regions for face and larynx in the persistent stuttering group. Contrary to previous findings in adults who stutter, no increases were found in the right hemisphere speech regions in stuttering or recovered children and no differences in right-left asymmetries. Instead, a risk for childhood stuttering was associated with deficiencies in left gray matter volume while reduced white matter integrity in the left hemisphere speech system was associated with persistent stuttering. Anatomical increases in right hemisphere structures previously found in adults who stutter may have resulted from a lifetime of stuttering. These findings point to the importance of considering the role of neuroplasticity during development when studying persistent forms of developmental disorders in adults.