A 3D biomechanical vocal tract model to study speech production control: How to take into account the gravity?

This paper presents a modeling study of the way speech motor control can deal with gravity to achieve steady-state tongue positions. It is based on simulations carried out with the 3D biomechanical tongue model developed at ICP, which is now controlled with the Lambda model (Equilibrium-Point Hypothesis). The influence of short-delay orosensory feedback on posture stability is assessed by testing different muscle force/muscle length relationships (Invariant Characteristics). Muscle activation patterns necessary to maintain the tongue in a schwa position are proposed, and the relations of head position, tongue shape and muscle activations are analyzed

Use of a biomechanical tongue model to predict the impact of tongue surgery on speech production

This paper presents predictions of the consequences of tongue surgery on speech production. For this purpose, a 3D finite element model of the tongue is used that represents this articulator as a deformable structure in which tongue muscles anatomy is realistically described. Two examples of tongue surgery, which are common in the treatment of cancers of the oral cavity, are modelled, namely a hemiglossectomy and a large resection of the mouth floor. In both cases, three kinds of possible reconstruction are simulated, assuming flaps with different stiffness. Predictions are computed for the cardinal vowels /i, a, u/ in the absence of any compensatory strategy, i.e. with the same motor commands as the one associated with the production of these vowels in non-pathological conditions. The estimated vocal tract area functions and the corresponding formants are compared to the ones obtained under normal condition

Modeling the consequences of tongue surgery on tongue mobility

This paper presents the current achievements of a long term project aiming at predicting and assessing the impact of tongue and mouth floor surgery on tongue mobility. The ultimate objective of this project is the design of a software with which surgeons should be able (1) to design a 3D biomechanical model of the tongue and of the mouth floor that matches the anatomical characteristics of each patient specific oral cavity, (2) to simulate the anatomical changes induced by the surgery and the possible reconstruction, and (3) to quantitatively predict and assess the consequences of these anatomical changes on tongue mobility and speech production after surgery

Activations musculaires et mouvements linguaux : modélisation en parole naturelle et pathologique

The purpose of the work presented in this manuscript is the development, in the long run, of some interactive software for tongue surgery, based on a three-dimensional biomechanical model of the tongue, allowing the evaluation of the consequences of some surgery on tongue mobility and supporting the planning and the per-operational guidance of the surgical gesture. The studies led to date aim at studying the feasibility of such a tool. The first part of this thesis is devoted to a thorough description of the model used. After the presentation of the vocal tract anatomy and of the clinical context, the model geometry is described with precision (internal structure of the tongue model and representation of the bony and soft structures of the vocal tract). The assumptions carried out for biomechanical modelling are introduced as well as the motor control scheme based on the lambda model of the equilibrium-point hypothesis. The extraction of the vocal tract area function is then presented with the model of speech synthesis. The second part is centred on the results obtained for natural and pathological speech. Our simulations showed the ability of our model to generate the oral vowels of French, with acoustic characteristics close to the values generally observed and satisfactory tongue shapes. Similar simulations are also presented for two cases of tongue surgery: a hemiglossectomy and a widened mouth floor resection.Les travaux présentés dans ce mémoire ont pour but, à long terme, l'élaboration d'un outil interactif pour la chirurgie linguale, basé sur un modèle biomécanique tridimensionnel de la langue, et permettant à la fois d'évaluer les conséquences d'une chirurgie sur la mobilité linguale et de favoriser le planning et le guidage per-opératoire du geste chirurgical. Les études conduites à ce jour visent à étudier la faisabilité d'un tel outil.La première partie de ce mémoire est consacrée à une description approfondie du modèle utilisé. Après une présentation de l'anatomie du conduit vocal et du contexte clinique, la géométrie du modèle est décrite avec précision (structure interne du modèle de langue et représentation des structures osseuses et molles du conduit vocal) ainsi que les hypothèses effectuées tant sur le plan de la modélisation biomécanique à l'aide d'un modèle hyperélastique que du contrôle moteur basé sur le modèle lambda du point d'équilibre. L'extraction de la filière aérique est alors introduite de même que le modèle de synthèse utilisé.La seconde partie est centrée sur les résultats obtenus en parole naturelle et en parole pathologique. Les simulations réalisées ont permis de montrer que ce modèle était capable de générer les voyelles orales du français, avec des caractéristiques acoustiques proches des valeurs généralement observées et des formes de langue satisfaisantes. Des simulations similaires sont également présentées pour deux cas de chirurgie linguale : une hémiglossectomie et une résection élargie du plancher buccal

A biomechanical model of cardinal vowel production: muscle activations and the impact of gravity on tongue positioning

International audienceA 3D biomechanical model of the tongue and the oral cavity, controlled by a functional model of muscle force generation (-model of the equilibrium point hypothesis) and coupled with an acoustic model, was exploited to study the activation of the tongue and mouth floor muscles during the production of French cardinal vowels. The selection of the motor commands to control the tongue and the mouth floor muscles was based on literature data, such as electromyographic (EMG), electropalatographic (EPG) and cineradiographic data. The tongue shapes were also compared to data obtained from the speaker used to build the model. 3D modeling offered the opportunity to investigate the role of the transversalis, in particular its involvement in the production of high front vowels. It was found, with this model, to be indirect via reflex mechanisms due to the activation of surrounding muscles, not voluntary. For vowel /i/, local motor command variations for the main tongue muscles revealed a non-negligible modification of the alveolar groove in contradiction to the saturation effect hypothesis, due to the role of the anterior genioglossus. Finally, the impact of subject position (supine or upright) on the production of French cardinal vowels was explored and found to be negligible

Muscle saturation effect in /i/ production: Counterevidence from a 3D biomechanical model of the tongue

Journal of Acoustical Society of America 123, 5(2) (2008) p. 3321International audienceNumerous works suppose the existence of a saturation effect to facilitate the control of the constriction area when producing vowel \i\. This study exploits a 3D biomechanical Finite Element model of the vocal tract to evaluate the effectiveness of this assumption. The model includes the tongue and its major muscles, represented as a hyperelastic body, inserted in the oral cavity including jaw, palate, pharyngeal walls and hyoid bone. Muscles activations are controlled with the lambda model (Equilibrium-Point Hypothesis). After determining a set of possible motor commands to generate vowel \i\, the impact of local variations of these commands on tongue shape was studied. The main tongue muscles motor commands were independently modified (by ,2%, 5%, 8% around their values at target) and the effect on the tongue shape and on the acoustic signal was studied. The simulations showed a global stabilization of the tongue body, thanks to the palatal contacts, but also variability in the alveolar groove due to the anterior genioglossus activation. Though extremely localized, this variation has an important impact on the constriction size and, then, on the acoustic signal. Consequently, a specific control of the articulatory variability could be necessary to explain experimental data for vowel \i\

Activations musculaires et mouvements linguaux : modélisation en parole naturelle et pathologique

Les travaux présentés dans ce mémoire ont pour but, à long terme, l élaboration d un outil interactif pour la chirurgie linguale, basé sur un modèle biomécanique tridimensionnel de la langue, et permettant à la fois d évaluer les conséquences d une chirurgie sur la mobilité linguale et de favoriser le planning et le guidage per-opératoire du geste chirurgical. Les études conduites à ce jour visent à étudier la faisabilité d un tel outil. La première partie de ce mémoire est consacre e à une description approfondie du modèle utilisé. Après une présentation de l anatomie du conduit vocal et du contexte clinique, la géométrie du modèle est décrite avec précision (structure interne du modèle de langue et représentation des structures osseuses et molles du conduit vocal) ainsi que les hypothèses effectuées tant sur le plan de la modélisation biomécanique à l aide d un modèle hyperélastique que du contrôle moteur basé sur le modèle lambda du point d équilibre. L extraction de la filière aérique est alors introduite de même que le modèle de synthèse utilisé. La seconde partie est centrée sur les résultats obtenus en parole naturelle et en parole pathologique. Les simulations réalisées ont permis de montrer que ce modèle était capable de générer les voyelles orales du français, avec des caractéristiques acoustiques proches des valeurs généralement observées et des formes de langue satisfaisantes. Des simulations similaires sont également présentées pour deux cas de chirurgie linguale : une hémiglossectomie et une résection élargie du plancher buccal.The purpose of the work presented in this manuscript is the development, in the long run, of some interactive software for tongue surgery, based on a three-dimensional biomechanical model of the tongue, allowing the evaluation of the consequences of some surgery on tongue mobility and supporting the planning and the per-operational guidance of the surgical gesture. The studies led to date aim at studying the feasibility of such a tool. The first part of this thesis is devoted to a thorough description of the model used. After the presentation of the vocal tract anatomy and of the clinical context, the model geometry is described with precision (internal structure of the tongue model and representation of the bony and soft structures of the vocal tract). The assumptions carried out for biomechanical modelling are introduced as well as the motor control scheme based on the lambda model of the equilibrium-point hypothesis. The extraction of the vocal tract area function is then presented with the model of speech synthesis. The second part is centred on the results obtained for natural and pathological speech. Our simulations showed the ability of our model to generate the oral vowels of French, with acoustic characteristics close to the values generally observed and satisfactory tongue shapes. Similar simulations are also presented for two cases of tongue surgery: a hemiglossectomy and a widened mouth floor resection.GRENOBLE1-BU Sciences (384212103) / SudocGRENOBLE-GIPSA-lab (384212301) / SudocSudocFranceF

To what extent does Tagged-MRI technique allow to infer tongue muscles' activation pattern? A modelling study

International audience`Tagged MRI' techniques have been used during the past years to predict which muscles are activated during the production tongue movements. Using this technique, inferences are based on the hypothesis that a significant strain of the anatomical region of a tongue muscle is evidence of voluntary muscle activation. In this paper, we propose to use a 3D finite-element biomechanical model of the oral cavity to study the relation between the distribution of the strains observed in the tongue body and the location of the tongue muscles activated either by the central nervous system or through reflex loops. Results showed in most cases a good correlation between the location of the tongue area that underwent high strains and the location of the muscle activated when studying single muscle activation. However, for movements involving combined muscle activations, a limited and even no correlation is measured. Hence, direct reading of Tagged MRI images would not allow inferring major tongue muscles activated in theses cases

To what extent does Tagged-MRI technique allow to infer tongue muscles' activation pattern? A modelling study

International audience`Tagged MRI' techniques have been used during the past years to predict which muscles are activated during the production tongue movements. Using this technique, inferences are based on the hypothesis that a significant strain of the anatomical region of a tongue muscle is evidence of voluntary muscle activation. In this paper, we propose to use a 3D finite-element biomechanical model of the oral cavity to study the relation between the distribution of the strains observed in the tongue body and the location of the tongue muscles activated either by the central nervous system or through reflex loops. Results showed in most cases a good correlation between the location of the tongue area that underwent high strains and the location of the muscle activated when studying single muscle activation. However, for movements involving combined muscle activations, a limited and even no correlation is measured. Hence, direct reading of Tagged MRI images would not allow inferring major tongue muscles activated in theses cases