Abstract
Auditory and somatosensory systems play a key role in speech motor control. In the act of speaking, segmental speech movements are programmed to reach phonemic sensory goals, which in turn are used to estimate actual sensory feedback in order to further control production. The adult's tendency to automatically imitate a number of acoustic-phonetic characteristics in another speaker's speech however suggests that speech production not only relies on the intended phonemic sensory goals and actual sensory feedback but also on the processing of external speech inputs. These online adaptive changes in speech production, or phonetic convergence effects, are thought to facilitate conversational exchange by contributing to setting a common perceptuo-motor ground between the speaker and the listener. In line with previous studies on phonetic convergence, we here demonstrate, in a non-interactive situation of communication, online unintentional and voluntary imitative changes in relevant acoustic features of acoustic vowel targets (fundamental and first formant frequencies) during speech production and imitation. In addition, perceptuo-motor recalibration processes, or after-effects, occurred not only after vowel production and imitation but also after auditory categorization of the acoustic vowel targets. Altogether, these findings demonstrate adaptive plasticity of phonemic sensory-motor goals and suggest that, apart from sensory-motor knowledge, speech production continuously draws on perceptual learning from the external speech environment.
Highlights
Speech production is a complex multistage motor process that requires phonetic encoding, initiation and coordination of sequences of supra-laryngeal and laryngeal movements produced by the combined actions of the pulmonary/respiratory system, the larynx and the vocal tract
For both F0 and F1 slope coefficients, the remaining data were entered into analyses of variance (ANOVA) with the experiment and the acoustic space congruency as between-subject variables
Influential models of speech motor control postulate a key role for on-line auditory and somatosensory feedback control mechanisms in speech production and highlight the sensorymotor nature of speech representations
Summary
Speech production is a complex multistage motor process that requires phonetic encoding, initiation and coordination of sequences of supra-laryngeal and laryngeal movements produced by the combined actions of the pulmonary/respiratory system, the larynx and the vocal tract. Influential models of speech motor control postulate that auditory and somatosensory representations play a key role in speech production. It is proposed that segmental speech movements are programmed to reach phonemic auditory and somatosensory goals, which in turn are used to estimate actual sensory inputs during speech production (for reviews, Perkell et al, 1997, 2000; Perrier, 2005, 2012; Guenther, 2006; Guenther and Vladusich, 2012; Perkell, 2012). In adult/fluent speech production, a large number of studies employing manipulations of both somatosensory and auditory feedback support the hypothesis that sensory feedback plays an important role in tuning speech motor control. Auditory information is often assumed to be the dominant sensory modality, the integration of somatosensory information in www.frontiersin.org
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