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An Examination of the Somatosensory Precision Requirements of Speech Production
Sazzad Nasir and David J. Ostry

Interest to date in precision in speech production has focused on issues related to auditory information. In the present paper we provide evidence that somatosensory information is also important in achieving the precision requirements of speech. We used a robotic device to apply lateral loads to the jaw that altered the jaw’s motion path and hence somatosensory feedback during speech production. The loads were applied during either the consonant or vowel-related phase of an utterance but had no measurable effect on the acoustics. With training, subjects were observed to correct for the load such that the motion path approached that normally experienced under no load conditions. Adaptation was observed in different amounts for both vowels and consonants depending on the utterance. An analysis of kinematic variability in trials without load indicated that compensation was greater in those phases of utterances that were less variable to begin with. The findings suggest that somatosensory precision does not depend on whether a movement is associated with vowel or consonant production per se. Given the patterns of adaptation that were observed in this study, it appears that speech movements differ in terms of their somatosensory precision requirements and these requirements are reflected in normal patterns of kinematic variation.

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