Temporal variability in sung productions of adolescents who stutter

How Does Prosodic Prominence Impact Articulatory Movement Parameters and Movement Variability in Adults Who Stutter?

PURPOSE

This study examined how focus-induced changes in degree of prosodic prominence impact articulatory movement parameters and movement variability in adults who stutter (AWS) and adults who do not stutter (AWNS). AWS were predicted to display greater across-trial variability in closing and opening duration, displacement, and velocity compared to AWNS as prosodic demands (i.e., addition of pitch accent, degree of prosodic strengthening) increased.

METHOD

Sixteen AWS and 15 AWNS participated in this study. A question-answer paradigm was used to manipulate the prosodic structure of spoken sentences through changes in semantic focus, and articulatory movement data were collected via a motion capture system. Kinematic analyses included oral closing and opening duration, displacement, and peak velocity, as well as the variability of these measures across repeated productions.

RESULTS

AWS and AWNS demonstrated prosodic strengthening of closing and opening gestures, contributing to the differentiation of non-focused and focused words, as well as different focus types (e.g., broad vs. narrow/contrastive). AWS demonstrated greater variability in closing displacement and velocity for unaccented, non-focused forms compared to other focus types and compared to AWNS, which was not in line with predictions.

CONCLUSIONS

This work demonstrates a complex relationship between degree of prosodic prominence and articulatory movement variability. Based on patterns observed in AWS, but not AWNS, it is plausible that processes involved in suppressing default nuclear accents could act as linguistic stressors on the speech motor systems of AWS. Further research is needed to advance our understanding of the role of prosody within a multifactorial view of stuttering.

From Sound to Movement: Mapping the Neural Mechanisms of Auditory-Motor Entrainment and Synchronization

BACKGROUND

Humans exhibit a remarkable ability to synchronize their actions with external auditory stimuli through a process called auditory-motor or rhythmic entrainment. Positive effects of rhythmic entrainment have been demonstrated in adults with neurological movement disorders, yet the neural substrates supporting the transformation of auditory input into timed rhythmic motor outputs are not fully understood. We aimed to systematically map and synthesize the research on the neural correlates of auditory-motor entrainment and synchronization.

METHODS

Following the PRISMA-ScR guidelines for scoping reviews, a systematic search was conducted across four databases (MEDLINE, Embase, PsycInfo, and Scopus) for articles published between 2013 and 2023.

RESULTS

From an initial return of 1430 records, 22 studies met the inclusion criteria and were synthesized based on the neuroimaging modality. There is converging evidence that auditory-motor synchronization engages bilateral cortical and subcortical networks, including the supplementary motor area, premotor cortex, ventrolateral prefrontal cortex, basal ganglia, and cerebellum. Specifically, the supplementary motor area and the basal ganglia are essential for beat-based timing and internally guided rhythmic movements, while the cerebellum plays an important role in tracking and processing complex rhythmic patterns and synchronizing to the external beat. Self-paced tapping is associated with additional activations in the prefrontal cortex and the basal ganglia, suggesting that tapping in the absence of auditory cues requires more neural resources. Lastly, existing studies indicate that movement rate and the type of music further modulate the EEG power in the alpha and beta frequency bands.

CONCLUSIONS

These findings are discussed in the context of clinical implications and rhythm-based therapies.

Knowns and unknowns about the neurobiology of stuttering

Stuttering occurs in early childhood during a dynamic phase of brain and behavioral development. The latest studies examining children at ages close to this critical developmental period have identified early brain alterations that are most likely linked to stuttering, while spontaneous recovery appears related to increased inter-area connectivity. By contrast, therapy-driven improvement in adults is associated with a functional reorganization within and beyond the speech network. The etiology of stuttering, however, remains enigmatic. This Unsolved Mystery highlights critical questions and points to neuroimaging findings that could inspire future research to uncover how genetics, interacting neural hierarchies, social context, and reward circuitry contribute to the many facets of stuttering.

Temporal organization of syllables in paced and unpaced speech in children and adolescents who stutter

PURPOSE

Speaking with an external rhythm has a tremendous fluency-enhancing effect in people who stutter. The aim of the present study is to examine whether syllabic timing related to articulatory timing (c-center) would differ between children and adolescents who stutter and a matched control group in an unpaced vs. a paced condition.

METHODS

We recorded 48 German-speaking children and adolescents who stutter and a matched control group reading monosyllabic words with and without a metronome (unpaced and paced condition). Analyses were conducted on four minimal pairs that differed in onset complexity (simple vs. complex). The following acoustic correlates of a c-center effect were analyzed: vowel and consonant compression, acoustic intervals (time from c-center, left-edge, and right-edge to an anchor-point), and relative standard deviations of these intervals.

RESULTS

Both groups show acoustic correlates of a c-center effect (consonant compression, vowel compression, c-center organization, and more stable c-center intervals), independently of condition. However, the group who stutters had a more pronounced consonant compression effect. The metronome did not significantly affect syllabic organization but interval stability improved in the paced condition in both groups.

CONCLUSION

Children and adolescents who stutter and matched controls have a similar syllable organization, related to articulatory timing, regardless of paced or unpaced speech. However, consonant onset timing differs between the group who stutters and the control group; this is a promising basis for conducting an articulatory study in which articulatory (gestural) timing can be examined in more detail.

Is atypical rhythm a risk factor for developmental speech and language disorders?

Although a growing literature points to substantial variation in speech/language abilities related to individual differences in musical abilities, mainstream models of communication sciences and disorders have not yet incorporated these individual differences into childhood speech/language development. This article reviews three sources of evidence in a comprehensive body of research aligning with three main themes: (a) associations between musical rhythm and speech/language processing, (b) musical rhythm in children with developmental speech/language disorders and common comorbid attentional and motor disorders, and (c) individual differences in mechanisms underlying rhythm processing in infants and their relationship with later speech/language development. In light of converging evidence on associations between musical rhythm and speech/language processing, we propose the Atypical Rhythm Risk Hypothesis, which posits that individuals with atypical rhythm are at higher risk for developmental speech/language disorders. The hypothesis is framed within the larger epidemiological literature in which recent methodological advances allow for large-scale testing of shared underlying biology across clinically distinct disorders. A series of predictions for future work testing the Atypical Rhythm Risk Hypothesis are outlined. We suggest that if a significant body of evidence is found to support this hypothesis, we can envision new risk factor models that incorporate atypical rhythm to predict the risk of developing speech/language disorders. Given the high prevalence of speech/language disorders in the population and the negative long-term social and economic consequences of gaps in identifying children at-risk, these new lines of research could potentially positively impact access to early identification and treatment. This article is categorized under: Linguistics > Language in Mind and Brain Neuroscience > Development Linguistics > Language Acquisition.

Infants Segment Words from Songs-An EEG Study

Children's songs are omnipresent and highly attractive stimuli in infants' input. Previous work suggests that infants process linguistic-phonetic information from simplified sung melodies. The present study investigated whether infants learn words from ecologically valid children's songs. Testing 40 Dutch-learning 10-month-olds in a familiarization-then-test electroencephalography (EEG) paradigm, this study asked whether infants can segment repeated target words embedded in songs during familiarization and subsequently recognize those words in continuous speech in the test phase. To replicate previous speech work and compare segmentation across modalities, infants participated in both song and speech sessions. Results showed a positive event-related potential (ERP) familiarity effect to the final compared to the first target occurrences during both song and speech familiarization. No evidence was found for word recognition in the test phase following either song or speech. Comparisons across the stimuli of the present and a comparable previous study suggested that acoustic prominence and speech rate may have contributed to the polarity of the ERP familiarity effect and its absence in the test phase. Overall, the present study provides evidence that 10-month-old infants can segment words embedded in songs, and it raises questions about the acoustic and other factors that enable or hinder infant word segmentation from songs and speech.

Timing variability of sensorimotor integration during vocalization in individuals who stutter

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

Comparação da performance de fala em indivíduos gagos e fluentes

RESUMO Objetivo O objetivo do estudo foi comparar a performance de fala do indivíduo com gagueira e do indivíduo fluente em tarefa de fala espontânea, tarefa de fala automática e a tarefa de canto. Método Participaram deste estudo 34 adultos, 17 com gagueira e 17 fluentes, pareados por gênero e idade. O estudo comparou o desempenho dos participantes em três tarefas de fala: monólogo, fala automática e canto. Foi analisado o número total de rupturas comuns e gagas. Resultados A tarefa de monólogo foi a única que apresentou diferenças estatisticamente significativas, tanto nas comparações intragrupos quanto nas comparações intergrupos. Conclusão O estudo mostrou que tarefas de maior complexidade motora e melódica, como a tarefa de monólogo, prejudica a fluência da fala, tanto em indivíduos com gagueira quanto em indivíduos fluentes.