Multisensory integration (MSI) allows us to link sensory cues from multiple sources and plays a crucial role in speech development. However, it is not clear whether humans have an innate ability or whether repeated sensory input while the brain is maturing leads to efficient integration of sensory information in speech. We investigated the integration of auditory and somatosensory information in speech processing in a bimodal perceptual task in 15 young adults (age 19–30) and 14 children (age 5–6). The participants were asked to identify if the perceived target was the sound /e/ or /ø/. Half of the stimuli were presented under a unimodal condition with only auditory input. The other stimuli were presented under a bimodal condition with both auditory input and somatosensory input consisting of facial skin stretches provided by a robotic device, which mimics the articulation of the vowel /e/. The results indicate that the effect of somatosensory information on sound categorization was larger in adults than in children. This suggests that integration of auditory and somatosensory information evolves throughout the course of development.

Compared to conversational speech, clear speech is produced with longer vowel duration, greater intensity, increased contrasts between vowel categories, and decreased dispersion within vowel categories. Those acoustic correlates are produced by larger movements of the orofacial articulators, including visible (lips) and invisible (tongue) articulators. Thus, clear speech provides the listener with audible and visual cues that are used to increase the overall intelligibility of speech produced by the speaker. It is unclear how those cues are produced by visually impaired speakers who never had access to vision. In this paper, we investigate the acoustic and articulatory correlates of vowels in clear versus conversational speech, and in sighted and congenitally blind speakers. Participants were recorded using electroarticulography while producing multiple repetitions of the ten Quebec French oral vowels in carrier sentences in both speaking conditions. Articulatory variables (lip, jaw, and tongue positions) as well as acoustic variables (contrasts between vowels, within-vowel dispersion, pitch, duration, and intensity) were measured. Lip movements were larger when going from conversational to clear speech in sighted speakers only. On the other hand, tongue movements were affected to a larger extent in blind speakers compared to their sighted peers. These findings confirm that vision plays an important role in the maintenance of speech intelligibility.

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Studies have reported strong links between speech production and perception. We aimed to evaluate the role of long- and short-term auditory feedback alteration on speech production. Eleven adults with normal hearing (controls) and 17 cochlear implant (CI) users (7 pre-lingually deaf and 10 post-lingually deaf adults) were recruited. Short-term auditory feedback deprivation was induced by turning off the CI or by providing masking noise. Acoustic and articulatory measures were obtained during the production of /u/, with and without a tube inserted between the lips (perturbation), and with and without auditory feedback. F1 values were significantly different between the implant OFF and ON conditions for the pre-lingually deaf participants. In the absence of auditory feedback, the pre-lingually deaf participants moved the tongue more forward. Thus, a lack of normal auditory experience of speech may affect the internal representation of a vowel.

This study investigated the effects of visual deprivation on the relationship between speech perception and production by examining compensatory responses to real-time perturbations in auditory feedback. Specifically, acoustic and articulatory data were recorded while sighted and congenitally blind French speakers produced several repetitions of the vowel /ø/. At the acoustic level, blind speakers produced larger compensatory responses to altered vowels than their sighted peers. At the articulatory level, blind speakers also produced larger displacements of the upper lip, the tongue tip, and the tongue dorsum in compensatory responses. These findings suggest that blind speakers tolerate less discrepancy between actual and expected auditory feedback than sighted speakers. The study also suggests that sighted speakers have acquired more constrained somatosensory goals through the influence of visual cues perceived in face-to-face conversation, leading them to tolerate less discrepancy between expected and altered articulatory positions compared to blind speakers and thus resulting in smaller observed compensatory responses.

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Objective We aimed to investigate the production of contrastive emphasis in French-speaking 4-year-olds and adults. Based on previous work, we predicted that, due to their immature motor control abilities, preschool-aged children would produce smaller articulatory differences between emphasized and neutral syllables than adults. Method Ten 4-year-old children and 10 adult French speakers were recorded while repeating /bib/, /bub/, and /bab/ sequences in neutral and contrastive emphasis conditions. Synchronous recordings of tongue movements, lip and jaw positions, and speech signals were made. Lip positions and tongue shapes were analyzed; formant frequencies, amplitude, fundamental frequency, and duration were extracted from the acoustic signals; and between-vowel contrasts were calculated. Results Emphasized vowels were higher in pitch, intensity, and duration than their neutral counterparts in all participants. However, the effect of contrastive emphasis on lip position was smaller in children. Prosody did not affect tongue position in children, whereas it did in adults. As a result, children's productions were perceived less accurately than those of adults. Conclusion These findings suggest that 4-year-old children have not yet learned to produce hypoarticulated forms of phonemic goals to allow them to successfully contrast syllables and enhance prosodic saliency.

Objectives: The effects of increased speaking rates on vowels have been well documented in sighted adults. It has been reported that in fast speech, vowels are less widely spaced acoustically than in their citation form. Vowel space compression has also been reported in congenitally blind speakers. The objective of the study was to investigate the interaction of vision and speaking rate in adult speakers. Patients and Methods: Contrast distances between vowels were examined in conversational and fast speech produced by 10 congenitally blind and 10 sighted French-Canadian adults. Acoustic analyses were carried out. Results: Compared with the sighted speakers, in the fast speaking condition, the blind speakers produced more vowels with contrast along the height, place of articulation, and rounding features located within the auditory target regions typical of French vowels. Conclusion: Blind speakers relied more heavily than sighted speakers on auditory properties of vowels to maintain perceptual distinctiveness.