Model-based inverse estimation for active contraction stresses of tongue muscles using 3D surface shape in speech production

This paper presents a novel inverse estimation approach for the active contraction stresses of tongue muscles during speech. The proposed method is based on variational data assimilation using a mechanical tongue model and 3D tongue surface shapes for speech production. The mechanical tongue model c...

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Bibliographic Details
Published in:	Journal of biomechanics Vol. 64; pp. 69 - 76
Main Authors:	Koike, Narihiko, Ii, Satoshi, Yoshinaga, Tsukasa, Nozaki, Kazunori, Wada, Shigeo
Format:	Journal Article
Language:	English
Published:	United States Elsevier Ltd 07-11-2017 Elsevier Limited
Subjects:	Active contraction stress Adult Computed tomography Computer simulation Coordination Data collection Deformation Equilibrium equations Euclidean geometry Finite element method Humans Image enhancement Inverse analysis Inverse estimation Inverse problems Male Mathematical analysis Mathematical models Mechanical analysis Medical imaging Models, Biological Motor task performance Muscle contraction Muscle Contraction - physiology Muscles NMR Nonlinear deformation Nuclear magnetic resonance Phonetics Speech Speech - physiology Speech production Stresses Three dimensional models Tongue Tongue - physiology Tongue muscle Ultrasonic imaging Variational data assimilation Vowels Inverse analysis Speech production Active contraction stress Nonlinear deformation Tongue muscle Variational data assimilation
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Summary:	This paper presents a novel inverse estimation approach for the active contraction stresses of tongue muscles during speech. The proposed method is based on variational data assimilation using a mechanical tongue model and 3D tongue surface shapes for speech production. The mechanical tongue model considers nonlinear hyperelasticity, finite deformation, actual geometry from computed tomography (CT) images, and anisotropic active contraction by muscle fibers, the orientations of which are ideally determined using anatomical drawings. The tongue deformation is obtained by solving a stationary force-equilibrium equation using a finite element method. An inverse problem is established to find the combination of muscle contraction stresses that minimizes the Euclidean distance of the tongue surfaces between the mechanical analysis and CT results of speech production, where a signed-distance function represents the tongue surface. Our approach is validated through an ideal numerical example and extended to the real-world case of two Japanese vowels, /ʉ/ and /ɯ/. The results capture the target shape completely and provide an excellent estimation of the active contraction stresses in the ideal case, and exhibit similar tendencies as in previous observations and simulations for the actual vowel cases. The present approach can reveal the relative relationship among the muscle contraction stresses in similar utterances with different tongue shapes, and enables the investigation of the coordination of tongue muscles during speech using only the deformed tongue shape obtained from medical images. This will enhance our understanding of speech motor control.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	0021-9290 1873-2380
DOI:	10.1016/j.jbiomech.2017.09.008