Lucie Scarbel

The shadow of a doubt? Evidence for perceptuo-motor linkage during auditory and audiovisual close-shadowing

One classical argument in favor of a functional role of the motor system in speech perception comes from the close-shadowing task in which a subject has to identify and to repeat as quickly as possible an auditory speech stimulus. The fact that close-shadowing can occur very rapidly and much faster than manual identification of the speech target is taken to suggest that perceptually induced speech representations are already shaped in a motor-compatible format. Another argument is provided by audiovisual interactions often interpreted as referring to a multisensory-motor framework. In this study, we attempted to combine these two paradigms by testing whether the visual modality could speed motor response in a close-shadowing task. To this aim, both oral and manual responses were evaluated during the perception of auditory and audiovisual speech stimuli, clear or embedded in white noise. Overall, oral responses were faster than manual ones, but it also appeared that they were less accurate in noise, which suggests that motor representations evoked by the speech input could be rough at a first processing stage. In the presence of acoustic noise, the audiovisual modality led to both faster and more accurate responses than the auditory modality. No interaction was however, observed between modality and response. Altogether, these results are interpreted within a two-stage sensory-motor framework, in which the auditory and visual streams are integrated together and with internally generated motor representations before a final decision may be available.

Sensory-motor relationships in speech production in post-lingually deaf cochlear-implanted adults and normal-hearing seniors: Evidence from phonetic convergence and speech imitation

ABSTRACT Speech communication can be viewed as an interactive process involving a functional coupling between sensory and motor systems. One striking example comes from phonetic convergence, when speakers automatically tend to mimic their interlocutors speech during communicative interaction. The goal of this study was to investigate sensory‐motor linkage in speech production in postlingually deaf cochlear implanted participants and normal hearing elderly adults through phonetic convergence and imitation. To this aim, two vowel production tasks, with or without instruction to imitate an acoustic vowel, were proposed to three groups of young adults with normal hearing, elderly adults with normal hearing and post‐lingually deaf cochlear‐implanted patients. Measure of the deviation of each participants f0 from their own mean f0 was measured to evaluate the ability to converge to each acoustic target. Results: showed that cochlear‐implanted participants have the ability to converge to an acoustic target, both intentionally and unintentionally, albeit with a lower degree than young and elderly participants with normal hearing. By providing evidence for phonetic convergence and speech imitation, these results suggest that, as in young adults, perceptuo‐motor relationships are efficient in elderly adults with normal hearing and that cochlear‐implanted adults recovered significant perceptuo‐motor abilities following cochlear implantation. HIGHLIGHTSThis paper investigates sensory‐motor linkage in speech production.Two tasks of phonetic convergence and imitation were proposed.Participants were elderly adults and cochlear‐implanted patients.Results show ability to converge to an acoustic target for the two groups.Results suggest that sensory‐motor linkage is efficient in the two populations.

Auditory and Audiovisual Close-shadowing in Post-Lingually Deaf Cochlear-Implanted Patients and Normal-Hearing Elderly Adults

Objectives: The goal of this study was to determine the effect of auditory deprivation and age-related speech decline on perceptuo–motor abilities during speech processing in post-lingually deaf cochlear-implanted participants and in normal-hearing elderly (NHE) participants. Design: A close-shadowing experiment was carried out on 10 cochlear-implanted patients and on 10 NHE participants, with two groups of normal-hearing young participants as controls. To this end, participants had to categorize auditory and audiovisual syllables as quickly as possible, either manually or orally. Reaction times and percentages of correct responses were compared depending on response modes, stimulus modalities, and syllables. Results: Responses of cochlear-implanted subjects were globally slower and less accurate than those of both young and elderly normal-hearing people. Adding the visual modality was found to enhance performance for cochlear-implanted patients, whereas no significant effect was obtained for the NHE group. Critically, oral responses were faster than manual ones for all groups. In addition, for NHE participants, manual responses were more accurate than oral responses, as was the case for normal-hearing young participants when presented with noisy speech stimuli. Conclusions: Faster reaction times were observed for oral than for manual responses in all groups, suggesting that perceptuo–motor relationships were somewhat successfully functional after cochlear implantation and remain efficient in the NHE group. These results are in agreement with recent perceptuo–motor theories of speech perception. They are also supported by the theoretical assumption that implicit motor knowledge and motor representations partly constrain auditory speech processing. In this framework, oral responses would have been generated at an earlier stage of a sensorimotor loop, whereas manual responses would appear late, leading to slower but more accurate responses. The difference between oral and manual responses suggests that the perceptuo–motor loop is still effective for NHE subjects and also for cochlear-implanted participants, despite degraded global performance.