Exploring auditory-motor interactions in normal and disordered speech

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

Online control of articulation based on auditory feedback in normal Speech and stuttering : behavioral and modeling studies

Thesis (Ph. D.)--Harvard-MIT Program in Health Sciences and Technology, February 2012."February, 2012." Cataloged from PDF version of thesis.Includes bibliographical references (p. 185-209).Articulation of multisyllabic speech requires a high degree of accuracy in controlling the spatial (positional) and the temporal parameters of articulatory movements. In stuttering, a disorder of speech fluency, failures to meet these control requirements occur frequently, leading to dysfluencies such as sound repetitions and prolongations. Currently, little is known about the sensorimotor mechanisms underlying the control of multisyllabic articulation and how they break down in stuttering. This dissertation is focused on the interaction between multisyllabic articulation and auditory feedback (AF), the perception of one's own speech sounds during speech production, which has been shown previously to play important roles in quasi-static articulations as well as in the mechanisms of stuttering. To investigate this topic empirically, we developed a digital signal processing platform for introducing flexible online perturbations of time-varying formants in speakers' AF during speech production. This platform was in a series of perturbation experiments, in which we aimed separately at elucidating the role of AF in controlling the spatial and temporal parameters of multisyllabic articulation. Under these perturbations of AF, normal subjects showed small but significant and specific online adjustments in the spatial and temporal parameters of articulation, which provided first evidence for a role of AF in the online fine-tuning of articulatory trajectories. To model and explain these findings, we designed and tested sqDIVA, a computational model for the sensory feedback-based control of speech movement timing. Test results indicated that this new model accurately accounted for the spatiotemporal compensation patterns observed in the perturbation experiments. In addition, we investigated empirically how the AF-based online speech motor control differed between people who stutter (PWS) and normal speakers. The PWS group showed compensatory responses significantly smaller in magnitude and slower in onset compared to the control subjects' responses. This under-compensation to AF perturbation was observed for both quasi-static vowels and multisyllabic speech, and for both the spatial and temporal control of articulation. This abnormal sensorimotor performance supports the hypothesis that stuttering involves deficits in the rapid internal transformations between the auditory and motor domains, with important implications for the neural basis of this disorder.by Shanqing Cai.Ph.D

Adaptive auditory-motor control of the time-varying formant trajectories in vowels and its patterns of generalization

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 61-65).This thesis aims at elucidating the role of auditory feedback in the learning and planning of complex articulatory gestures in time-varying phonemes. To this end, we studied native Mandarin speakers' responses to perturbations of their auditory feedback of the first and second formant trajectories during the production of the Mandarin triphthong /iau/. On the group level, subjects adaptively adjusted their productions to partially compensate for the perturbations in auditory feedback under both the F1 and F2 perturbations. But considerable between-individual variation existed. The result indicate that auditory feedback-based learning and control of speech movements is not restricted to quasi-static gestures in monophthongs as found in previous studies, but also extends to time-varying gestures. To probe the internal structure of the mechanisms of auditory-motor transformations in speech, we tested the pattern of generalization of the adaptation trained on the triphthong /iau/ to other vowels with different spatial and temporal characteristics in the same language. A broad but weak and decaying pattern of generalization was observed under the F1 perturbation; the strength of the generalization diminished with increasing dissimilarity from /iau/. No significant transfer of adaptation was found under the perturbation of F2. The details and implications of the pattern of generalization are examined and discussed in light of previous sensorimotor adaptation studies of speech and limb motor control and a neurocomputational model of speech motor control.by Shanqing Cai.S.M

Impaired responses to time-shifting perturbations in adults who stutter during rhythmic and non-rhythmic speech

Supporting documentatio

Responses to intensity-shifted auditory feedback during running speech

PURPOSE: Responses to intensity perturbation during running speech were measured to understand whether prosodic features are controlled in an independent or integrated manner. METHOD: Nineteen English-speaking healthy adults (age range = 21-41 years) produced 480 sentences in which emphatic stress was placed on either the 1st or 2nd word. One participant group received an upward intensity perturbation during stressed word production, and the other group received a downward intensity perturbation. Compensations for perturbation were evaluated by comparing differences in participants' stressed and unstressed peak fundamental frequency (F0), peak intensity, and word duration during perturbed versus baseline trials. RESULTS: Significant increases in stressed-unstressed peak intensities were observed during the ramp and perturbation phases of the experiment in the downward group only. Compensations for F0 and duration did not reach significance for either group. CONCLUSIONS: Consistent with previous work, speakers appear sensitive to auditory perturbations that affect a desired linguistic goal. In contrast to previous work on F0 perturbation that supported an integrated-channel model of prosodic control, the current work only found evidence for intensity-specific compensation. This discrepancy may suggest different F0 and intensity control mechanisms, threshold-dependent prosodic modulation, or a combined control scheme.R01 DC002852 - NIDCD NIH HHS; R03 DC011159 - NIDCD NIH HH

Auditory feedback perturbation in adults and children

Auditory feedback plays an important role in speech motor learning. Experimental paradigms where auditory feedback is perturbed during speech production of children might give valuable insights in the role of auditory feedback in the acquisition of speech motor programs throughout development. Studies investigating auditory feedback in speech development suggest that crucial steps are made in the development of auditory-motor integration between the ages of 4 – 9 years, but thus far direct comparisons between different age groups are absent. In the present study, we investigated to what extent Dutch speaking children in this age span were able to compensate for and adapt to auditory feedback perturbations. Auditory feedback was perturbed by real-time shifting the first and second formant of the vowel /e/ during the production of CVC words. Preliminary results indicate that age is an important factor in the presence of stable compensation and adaptation effects. When comparing groups, both children and adults were able to compensate for perturbed auditory feedback, but the proportion of subjects displaying this effect was greater in the adult group. Furthermore, we will discuss experimental considerations and limitations of measuring on-line and off-line compensation for perturbed auditory feedback with very young speakers

Auditory-motor adaptation is reduced in adults who stutter but not in children who stutter

Previous studies have shown that adults who stutter produce smaller corrective motor responses to compensate for unexpected auditory perturbations in comparison to adults who do not stutter, suggesting that stuttering may be associated with deficits in integration of auditory feedback for online speech monitoring. In this study, we examined whether stuttering is also associated with deficiencies in integrating and using discrepancies between expect ed and received auditory feedback to adaptively update motor programs for accurate speech production. Using a sensorimotor adaptation paradigm, we measured adaptive speech responses to auditory formant frequency perturbations in adults and children who stutter and their matched nonstuttering controls. We found that the magnitude of the speech adaptive response for children who stutter did not differ from that of fluent children. However, the adaptation magnitude of adults who stutter in response to formant perturbation was significantly smaller than the adaptation magnitude of adults who do not stutter. Together these results indicate that stuttering is associated with deficits in integrating discrepancies between predicted and received auditory feedback to calibrate the speech production system in adults but not children. This auditory-motor integration deficit thus appears to be a compensatory effect that develops over years of stuttering

Providing Suggestions of Expanded Text from Abbreviated Text Input

This disclosure describes techniques to provide suggestions of expanded text from abbreviated or compressed text that has been input by a user. A language model is used to determine and present the most likely full words and phrases that match user intent based on the user’s abbreviated text input, such as the first letter of each word of a phrase and/or omission of one or more words of the phrase. The described techniques can greatly improve speed of text entry to devices via a keyboard or other input modality

Auditory feedback perturbation in children with developmental speech sound disorders

Several studies indicate a close relation between production symptoms and perceptual acuity in children with speech sound disorders (SSD). An important underlying factor here might be a reduced capacity to use auditory feedback. However, the mechanisms behind this relation are still poorly understood. The aim of this study was to investigate the ability to compensate and adapt for perturbed auditory feedback in children with SSD compared to age-matched normally developing children (age 4-8) to unravel the role of auditory feedback in the manifestation of SSD. 15 normally developing children aged 4.1-8.7 years (mean=5.5, SD=1.4), and 11 children with SSD aged 3.9-7.5 years (mean=5.1, SD=1.0) participated in the study. Auditory feedback was perturbed by real-time shifting the first and second formant of the vowel /e/ during the production of CVC words in a five-step paradigm (familiarization; baseline; ramp; hold; release). Preliminary results indicate a larger proportion of subjects responding to perturbation in children with SSD compared to the control group. However, in general the normally developing children showing a response were better able to compensate and adapt, adjusting their formant frequencies in the direction opposite to the perturbation where the majority of the children with SSD followed (amplifying) the perturbation

Discovery of a Unique Structural Motif in Lanthipeptide Synthetases for Substrate Binding and Interdomain Interactions

Class III lanthipeptide synthetases catalyze the formation of lanthionine/methyllanthionine and labionin crosslinks. We present here the 2.40 Å resolution structure of the kinase domain of a class III lanthipeptide synthetase CurKC from the biosynthesis of curvopeptin. A unique structural subunit for leader binding, named leader recognition domain (LRD), was identified. The LRD of CurKC is responsible for the recognition of the leader peptide and for mediating interactions between the lyase and kinase domains. LRDs are highly conserved among the kinase domains of class III and class IV lanthipeptide synthetases. The discovery of LRDs provides insight into the substrate recognition and domain organization in multidomain lanthipeptide synthetases