Keywords: Tongue/palate interaction, Speech Production, Swallowing, Pressure Sensing Palatography, Complete denture Interaction langue/palais, Production de la parole, Déglutition, Palatographie Capteur de pression, Prothèse Adjointe complète

The aim of the thesis is the study of the mechanical interaction between tongue and palate in speech production and swallowing. This interaction is crucial since it determines the shape of the tongue and its time evolution before and after contacts occur. Yet it cannot be studied with conventional kinematic approaches, since magnitude of movements is too small. The first part of the thesis was devoted to the design of an experimental setup to measure this interaction without perturbing the vocal tract. The first specificity is that the setup is used on subjects who are edentulous and wear a complete denture. We use a duplicate of the complete denture to insert miniature strain gauge sensors with enhanced response characteristics, that enable the measure of the mechanical pressure exerted by the tongue in different locations of the palate, without altering the shape of the palatal arch. The second specificity is that the calibration procedure uses a Dried Water Column (DWC) that applies pressure on the sensor via a deformable latex membrane, that simulates the way tongue touches the palate.

The second part of the thesis enabled the design of an experimental protocol aiming at (1) providing a characterization of the tongue-palate interaction in normal speech production and swallowing based on edentulous subjects whom we consider to have adapted to their complete denture (cohort 1), (2) observing the adaptation process in a longitudinal study of edentulous subjects who are new users of complete denture (cohort 2). This work includes for two cohorts the design of the subject inclusion criteria, the motor tasks and the statistical method for the data analysis. However, unforeseen long delays were faced in the application process for the ethical approval and no data were collected in this context.

Hence the third part of the thesis used data recorded in our most recent pilot study, with a French speaking edentulous adult. It is shown that our setup makes possible to tackle crucial theoretical questions in speech production such as the existence of virtual targets above the palate in stops or the role of the palate in the air channel shaping in fricatives. Results of swallowing tasks are less clear, but it is shown that precise time sequencing of contacts can be described, making possible the specification of how the ondulatory movements of the tongue in the oral phase of swallowing takes advantage of palatal contacts.

In conclusion implications of this thesis are presented for a functional assessment of complete dentures, and the design of dentures that would be adapted to each subject's specificities.

Résumé

L'objectif de cette thèse est l'étude des interactions mécaniques entre la langue et le palais dans la production de parole et la déglutition. Cette interaction est cruciale car elle détermine la morphologie de la langue et son évolution dans le temps avant et après les contacts. Elle ne peut cependant pas être étudiée avec des approches cinématiques conventionnelles, car l'amplitude des mouvements est trop faible.

La première partie de la thèse est consacrée à la conception d'un dispositif expérimental permettant de mesurer ces interactions sans perturber l'appareil vocal. La première particularité est que le dispositif est utilisé sur des patients édentés appareillés. Nous utilisons un duplicata de la prothèse complète maxillaire pour insérer des capteurs miniatures à jauges de contrainte dont les caractéristiques de réponse sont optimisées et qui permettent de mesurer la pression mécanique exercée par la langue sur le palais. La seconde particularité est qu'il existe une procédure d'étalonnage, associée aux capteurs, qui utilise une Colonne d'Eau Sèche. Elle applique une pression sur le capteur via une membrane en latex déformable, capable de simuler le comportement visco-élastique de la langue sur le palais.

La deuxième partie de la thèse décrit le protocole de recherche clinique visant à (1) caractériser l'interaction langue-palais au cours de la prononciation et de la déglutition normales sur des individus édentés que nous considérons adaptés à leur prothèse complète (Cohorte 1), (2) observer l'adaptation dans une étude longitudinale des patients édentés nouvellement appareillés (Cohorte 2). Ce projet comprend, pour les deux cohortes, la description des objectifs, le protocole expérimental, la description fine des paramètres pertinents et la méthode statistique de traitement des données. Toutefois, le processus de rédaction et de soumission de ce protocole à un Comité de Protection des Personnes (CPP) a été plus long que prévu et l'étude clinique n'a pu être menée dans le cadre de cette thèse.

C'est pourquoi, dans la troisième partie de la thèse, nous avons utilisé les données enregistrées dans l'étude de faisabilité, auprès d'un adulte édenté francophone. Les résultats montrent que notre dispositif permet d'explorer des hypothèses théoriques cruciales dans la parole comme l'existence de cibles virtuelles au-dessus du palais ou le rôle du palais dans la mise en forme du conduit aérien des consonnes fricatives. Les résultats des données enregistrées lors de la déglutition sont moins clairs, mais l'enchaînement temporel précis des contacts peut être décrit, ce qui permet de préciser comment les mouvements ondulatoires de la langue pendant la phase orale de la déglutition exploitent les contacts avec le palais.

INTRODUCTION

Researchers from various backgrounds have stated the role of tongue movements in a broad range of functional and developmental fields including craniofacial development, mastication, swallowing and articulation. Understanding the normal physiology and pathophysiology of swallowing and speech is important to understand and evaluate disorders of eating and speaking and to develop their rehabilitation strategies [START_REF] Matsuo | Anatomy and physiology of feeding and swallowing: normal and abnormal[END_REF].

Towards the end of the mastication, which breaks down the food into pieces, the tongue plays an important role in organizing the pieces into the bolus and subsequently, during the oral controlled phase of swallowing, by propelling it towards the pharynx in which the reflex phase of the swallowing starts that moves the bolus to the oesophagus and then to the stomach.

The tongue transports the bolus from the anterior of the oral cavity, back to the entrance of the oropharynx. In the oral phase of swallowing, the tongue uses contacts with the palate, both to seal the vocal tract and to reach the appropriate shape and its variation in time and space [START_REF] Dodds | The physiology of swallowing[END_REF]. Fundamental to this idea is the application of a force of the appropriate magnitude and timing as this not only initiates but also maintains bolus movement at an ideal speed and direction. Despite large development in understanding of the way food consistency and rheology, tongue posture, jaw movement, sex and age can significantly affect how food is swallowed [START_REF] Cheng | Dentofacial morphology and tongue function during swallowing[END_REF][START_REF] Nicosia | The fluid mechanics of bolus ejection from the oral cavity[END_REF][START_REF] Steele | The dynamics of lingual-mandibular coordination during liquid swallowing[END_REF][START_REF] Youmans | Measures of tongue function related to normal swallowing[END_REF], there remains an incomplete understanding of how we can assess the efficiency or disorders of the gestures, when swallowing process does not work well.

Although contact of tongue against the palate plays a vital role in swallowing and articulation, contact patterns are quite different in two. Speech is a learned practiced neuromuscular pattern which makes use of organs designed primarily for functions such as breathing and swallowing. Articulation is the crucial stage resulting in the production of speech sounds and consists of a series of movements by a set of organs of speech called the articulators.

A conventional approach to study speech motor control comprises of investigating the kinematic patterns of vocal tract articulators. The tongue is the principal articulator of the vocal tract, since hard palate is immobile, the tongue performs all the active shaping and constricting in the central part of the vocal tract which is crucial to formation of the sounds [START_REF] Stone | How the tongue takes advantage of the palate during speech[END_REF].

The tongue movements particularly for oral consonants are mostly produced in the presence of palatal contacts. The complexity of these contact patterns and the interaction between the contact and tongue configuration leads to the questions that why and how the tongue uses the palate to influence it kinematic properties required for speech movements. The role of palate in tongue shaping and positioning has already been studies in literature [START_REF] Fuchs | What role does the palate play in speech motor control? Insights from tongue kinematics for German alveolar obstruents[END_REF][START_REF] Fuchs | The role of the palate in tongue kinematics: an experimental assessment in VC sequences from EPG and EMMA data[END_REF]. Stone et al [START_REF] Stone | TOWARD A MODEL OF 3-DIMENSIONAL TONGUE MOVEMENT[END_REF] suggested that some tongue shapes particularly in alveolar production could not be produced in a free-standing position and are as a result of tongue pushing the palate. They also demonstrated that the tongue uses the stability provided by palatal contacts to coordinate its movement with the jaw movements [START_REF] Stone | How the tongue takes advantage of the palate during speech[END_REF], and by using tactile feedback and support given by tongue-palate contact create appropriate vocal tract shapes to control the airflows and pressure. All these studies shows that (1) the tongue-palate contact facilitates the production of tongue shapes, (2) the tongue may use tongue-palate contact to control the varying airflow and pressure required for speech and (3) the tongue may use the tactile information available through tongue-palate contact to modify its position and shape so that is can create suitable constriction necessary for speech.

Given the crucial role of palatal contacts for the tongue in the basic biological orofacial motor functions of humans, the changes of the interaction between tongue and palate introduced by dentures should not be underestimated. Indeed, dentures alter the morphology of the palatal arch, reduce the volume of the oral cavity and strongly reduce the tactile sensory feedback from the palate. As a matter of fact, behavioural studies have provided clear evidence that prosthodontic rehabilitation with complete dentures influences speech and swallowing performance directly or indirectly [START_REF] Furuya | Effects of wearing complete dentures on swallowing in the elderly[END_REF][START_REF] Palmer | Analysis of speech in prosthodontic practice[END_REF]. Since, tongue kinetics are dependent on the shape of surrounding structures, the intra-oral morphological change caused by wearing complete dentures can influence the tongue motor biomechanics. This hypothesis has been tested by several researchers using experimental denture who demonstrated that changes caused by wearing complete denture can distort speech sounds [START_REF] Petrović | Speech sound distortions caused by changes in complete denture morphology[END_REF], or reduce the swallowing efficiency [START_REF] Veyrune | Complete denture wearers: electromyography of mastication and texture perception whilst eating meat[END_REF]. However, no study has focused on accurately analysing the potential causal links between the morphology of the palatal plate and the emergence of difficulties in the articulation of speech and swallowing in edentulous patients with such prosthesis. During speech production, the tongue comes into contact with the plate in different manners depending on the sequence of vowels and consonants considered.

It can influence the stability of the prosthesis in a favourable manner or not. In the same way during swallowing, the positioning of the teeth in maximum intercuspation makes it possible to stabilize the prosthesis on its load bearing surfaces by harmoniously distributing the occlusal contacts and the tongue while taking load bearing on the palate necessary for the swallowing movement. Even though complete dentures have benefitted from the latest technological developments in the field of materials, their principles of their basic design and therapeutic use have remained the same [START_REF] Zarb | Prosthodontic Treatment for Edentulous Patients-E-Book: Complete Dentures and Implant-Supported Prostheses[END_REF]. We believe that this design could be significantly improved, for a better comfort of the patients and a better preservation of their basic biological orofacial motor functions, if we could have a precise knowledge of the spatial distribution and the time organization of the mechanical interaction between the tongue and the prosthesis. In our view, this could be an important step towards the specification of general principles for the design of maxillary complete denture, in order on the one hand to make during swallowing most of the tongue help stabilizing the prosthesis, and in the other hand to facilitate a good quality of speech.

That is why, we have designed an experimental method which confronts different aspects of research (clinical, mechanical, physiological, anatomical and cognitive) in order to study tongue motor control during speech production and swallowing. We introduce an innovative way of recording tongue pressures from multiple sites within the prosthesis, which could be worn during functional tasks without perturbation of vocal tract. This method relies on the use of strain gauge sensors, which reliability and accuracy have been extensively demonstrated, and to use the complete denture of edentulous patients to insert these sensors in the oral cavity. This design enables that the sensors minimally perturb the oral motor tasks of the edentulous patients, for whom the main challenge is to adapt to the denture, and not to the sensors. In this context, we want to address to main research questions:

1.

What are the normal spatial distribution and time organization of the tongue-to-palate mechanical pressure during speech and swallowing?

2.

How do edentulous patients, who just received their complete denture, adapt to it for swallowing and for speech?

3.

How can the study of tongue-palate contact help understand oro-motor disorders particularly in edentulous patients after glossectomy in designing the prosthesis to facilitate swallowing and speech?

To address these research questions, an important part of the work that has been done in the context of this thesis, is the design of the experimental protocol. To address the first question, we consider edentulous subjects for whom the process of adaptation to the denture has been completed, because they have been wearing their denture for more than 9 months.

These subjects will constitute the first cohort of participants to our experimental protocol. To address the second question, we consider a second cohort, made of edentulous patients who just received their complete denture and whom we will longitudinally observe during their process of adaptation to the denture. We have designed for these two cohorts a number of variables that we consider to be relevant to characterize the tongue-palate interactions in speech and swallowing, and specific statistical methods that enable to establish reference patterns for these interactions and to characterize adaptation over time to the denture. The beginning of the data collection required the application for the ethical agreement from the Comité de Protection des Personnes (CPP). We have worked on this application that is carried by the Hospices Civils de Lyon. However, this is a very long process and we did not yet get the agreement. For this reason, we could not implement the comprehensive methodology that we developed, and we can present in this manuscript only the results of a pilot study.

In this manuscript chapter "State of art about pressure sensing device" provides an overview of the literature related to the devices developed to evaluate the tongue-palate interactions. In chapter "Methodology", we discuss the objectives and the technical aspects of our experimental setup, explain which variables will be used to characterize the tongue-topalate pressure in relation with key-aspects of speech and swallowing motor functions, present the inclusion parameters for the two cohorts and introduce the statistical methods used to address our two research questions. In chapter "Results of pilot experiment" we present the data collected on a single subject during the speech production and swallowing pilot study, in order to show the kind of information that can be inferred from our experimental approach.

Finally, in the "Discussion and Conclusion" chapter we discuss the implications of the results obtained in pilot experiment, in particular in relation to their potential impact on the design of the complete denture.

STATE OF ART ABOUT PRESSURE SENSING DEVICE IN SPEECH AND SWALLOWING

2.1 Problems faced in investigating speech and swallowing

Measuring the articulatory behaviour determining the vocal tract shape is a difficult task, because the location of some of articulators inside the oral cavity makes the access to them quite challenging, and because the differences in their mechanical structures (hard versus soft) strongly influence the characteristics of their displacements (rotation or translation versus deformation). For example, the soft deformation of the tongue requires different measurement strategies compared to rigid body movements of the jaw. Also, structures that are visible by superficial inspection like the lips are much easier to record than structures inside the oral cavity such as the velum. Another difficulty faced is the interaction among articulators. Some articulators' behaviours are more correlated with each another than others, and identifying the separate contribution of each articulator to the vocal tract shape variation can be difficult. An example is the tongue-jaw system, as it is evident that jaw height is a major factor in tongue height. However, this pairing of the two articulators becomes increasingly weaker as one moves posteriorly until in pharynx. Thus, measuring the contribution of the jaw to tongue movement becomes a difficult task. Another example is the detection of contact locations between articulators. Measuring where contacts occur on the hard palate is quite easy and it has been done for years using a pseudo palate made of plastic. However, measuring where on the tongue contact occurs, would not be possible with such a device, as it would inhibit contraction, flexion, expansion and torsion of tongue surface. More generally instruments that are inserted into the mouth have to meet certain criteria. If they enter the oral cavity, they must not distort the speech articulation; thus, to be unobtrusive they must be stable against a surface), be small or positioned on non-contact surfaces (pellet tracking systems). They should not be affected by temperature change, moisture and air pressure. Designing devices that are non-invasive, nonobstructive and still capable to measure one or more components of speech and swallowing is difficult.

Types of instruments for measuring speech and swallowing

The main types of instruments developed for studying speech and swallowing physiology are imaging techniques, point-tracking techniques and measures of tongue-palate contacts.

Imaging techniques that are well known in speech research are X-ray, computed tomography

ELECTROPALATOGRAPHY (EPG)

EPG is a proven instrument to assess and treat articulatory disorders and allows the timing, location and patterns of tongue-palate contact patterns and their changes over time during speech production. It consists of a very thin custom made acrylic palatal plate embedded with series of miniature electrodes (Figure .2). A body electrode usually placed at wrist is used to pass a small sinusoidal signal. When the tongue contacts the electrodes, the circuit is completed and the electric signal is transmitted to external processing unit, which displays the contacts on a computer screen either in real time or over time, in series of EPG frames. EPG has been in use for more than three decades to study normal and speech disordered populations, including people with motor speech disorders , structural abnormalities (Korpijaakko-Huuhka, Söderholm, & Lehtihalmes, 1999), hearing disorders and children with developmental speech impairment [START_REF] Carter | EPG therapy for children with long-standing speech disorders: Predictions and outcomes[END_REF][START_REF] Gibbon | Changes in linguapalatal contact patterns during therapy for velar fronting in a 10-year-old with Down's syndrome[END_REF]. EPG has been exploited in linguistics from many perspectives. These works include: aspects of articulatory description of sounds involving lingual articulation across languages, articulatory characterization of fricatives [START_REF] Hoole | A comparative investigation of coarticulation in fricatives: Electropalatographic, electromagnetic, and acoustic data[END_REF], lingual coarticulation It has also been extensively used in assessments and treatments of speech disorders which including cleft palate, glossectomy [START_REF] Imai | Articulatory function after resection of the tongue and floor of the mouth: palatometric and perceptual evaluation[END_REF], occlusal disorders [START_REF] Suzuki | The articulatory characteristics of the tongue in anterior openbite: observation by use of dynamic palatography[END_REF], compensation to changes in oral morphology [START_REF] Hamlet | Compensatory alveolar consonant production induced by wearing a dental prosthesis[END_REF]. It has also been used as bio-feedback for vowel teaching in profoundly hearing-impaired patients [START_REF] Fletcher | Teaching consonants to profoundly hearing-impaired speakers using palatometry[END_REF]. The magnitude of the EPG information are rich spatially because of the density of the sensors on the palate. However, the quantality of the measure (contact versus no contact) limits the description of the contact strength [START_REF] Wrench | Advances in EPG palate design[END_REF]. When there is little contact (less electrodes are active) we can only guess that the magnitude of the pressure is small where when there is more contact (most of electrodes are active) we can assume that pressure is large. The quantality of the measure (contact versus no contact) limits the description of the variation in contact strength. The data only provides information when and where the tongue touches the palate but not how strong the contact is. The second, is instrumental drawback is the palatal plate can be intrusive to the articulation, research has shown that presence of artificial plate has resulted in significant changes to articulation of consonants [START_REF] Mcauliffe | Influence of a standard electropalatography artificial palate upon articulation[END_REF].

PRESSURE SENSING PALATOGRAPHY (PPG)

Even though the advancement of a device to measure dynamic pressure sensing represents a new step in EPG devices' design, the idea of measuring tongue pressure is by no means a new one. The first attempts date back to the 60s [START_REF] Proffit | EVALUATION OF TONGUE PRESSURES DURING SPEECH[END_REF], but the development of such devices have experienced a strong upsurge in the last fifteen years, mainly in the context of the investigation of swallowing and its disorders. A number of devices, also called "Pressure Sensing Electropalatographs" [START_REF] Hori | Newly developed sensor sheet for measuring tongue pressure during swallowing[END_REF][START_REF] Martin | Introducing the pressure-sensing palatograph-the next frontier in electropalatography[END_REF][START_REF] Murdoch | Physiological investigation of dysarthria: recent advances[END_REF] have been designed in the past to record dynamic tongue-to-palate pressures, during either speech production or swallowing. The commonly used devices are divided into 3 categories: (1) air bulbs (KayPentax Digital Swallowing Workstation, KayPentax,Lincoln Park, NJ) [START_REF] Todd | Isometric and swallowing tongue strength in healthy adults[END_REF]; (2) sensor sheets with resistive sensors [START_REF] Hori | Newly developed sensor sheet for measuring tongue pressure during swallowing[END_REF][START_REF] Wakumoto | A pressure sensitive palatography: Application of new pressure sensitive sheet for measuring tonguepalatal contact pressure[END_REF] or with capacitive sensors (Tiede, Perkell, Zandipour, Matthies, & Stockmann, 2003); (3) palatal plates with embedded pressure sensors [START_REF] Jeannin | Tongue pressure recordings during speech using complete denture[END_REF][START_REF] Ono | Clinical application of tongue pressure measurement during mastication and swallowing[END_REF]. [START_REF] Robin | System and method for detecting pressure of selected body parts[END_REF]) developed a portable pressure measuring device which employed a fluid-filled bulb of a suitable size to fit within the mouth of a person to sense pressure generated. A sensor is connected with the bulb for converting the pressure sensed by the bulb to an electrical signal. The fluid-filled bulb is quite resilient and deforms under the pressure in order to measure the pressure generated and thereafter return to original shape when pressure is removed (Figure .2). The sensor converts the pressure to an electric signal. An output display responsive to the electrical signal of sensor provided the pressure. The Iowa Oral Performance Instrument (IOPI) is a second version of the instrument designed by Robin &

Bulbs filled with air/fluid

Luschei. The difference is that the IOPI's bulb is filled with air. IOPI is commercially available and it is one of the most widely used now in tongue pressure investigations.

Bu Sha [START_REF] Sha | Force production of the genioglossus as a function of muscle length in normal humans[END_REF] used a custom-designed lingual pressure transducer housed in a piece of polyvinyl chloride tubing. The tube was bisected lengthwise, and a latex balloon catheter was mounted between the two halves of tubing and secured in place with the dental impression material. The balloon catheter was connected to a strain gauge transducer (Gould Instruments, Cleveland, OH) and the output was amplified and recorded on a computer. The balloon was positioned so that, when it was inflated with 4 ml of saline, it protruded 1.0 cm beyond the end of the tube (Figure .3). A rubber sheath of 2 mm thickness covered the end of the tube to provide a soft, stable surface to bite when producing protrusion efforts. The maximum tongue force recorded was 28.0 ± 2.0 N. fitted with a small, partially inflated balloon made from medical grade latex, a plastic pipe as a connector length = 8.5 mm, internal diameter = 4.7 mm, external diameter = 0.5 mm, thickness = 0.5 mm), and a 1-ml tuberculin test syringe cylinder for the patient to hold on to it (Figure 5). The balloon was connected to a manometer, it works on the principle of hydrostatic equilibrium which states that the pressure at any point in a fluid at rest is equal, and its value is just the weight of the overlying fluid. The maximum pressure was between 31.9 to 42 kPa. For patient to hold on to (C) [START_REF] Utanohara | Standard values of maximum tongue pressure taken using newly developed disposable tongue pressure measurement device[END_REF].

Sensor sheets system

Wakumoto, Masaki, & Ooue, 2003 proposed a palatal plate with the shape of the user's palate in which resistive pressure sensor array sheet were attached on the surface of the palatal plate with a biocompatible adhesive. The thickness of the palatal plate and the sensor sheet was about 0.5 mm and 0.1 mm thick respectively so as not to interfere with normal speech production and to be robust enough to maintain its shape accurately (Figure 6). The principle behind measuring the tongue pressure was based on sense a change in the distance between a pair of thin sheet electrodes by measuring the electrical resistance of the "pressure sensitive ink" between the two electrodes. The authors measured the tongue pressure from 10 Japanese subjects during stop consonants /t/ and /d/ and the results showed stronger palatal contact for /t/ than that for /d/.

Figure.

6. An example of resistive sensor sheets arrangement by Wakumoto et al.

A T-shaped pressure sensor sheet with five measuring points was developed by for measuring the tongue pressure during swallowing. This sensor sheet was attached directly to palatal mucosa with a denture adhesive and the thickness of the sensor sheet was about 0.1 mm (Figure .7). The sensor sheet was available in three sizes; small, medium and large. The results on 30 subjects in measuring maximum tongue pressure during water swallowing showed that the output value of sensor sheet was lower than the pressure sensors [START_REF] Hori | Newly developed sensor sheet for measuring tongue pressure during swallowing[END_REF].

Figure .7. An example of resistive sensor sheet for measuring tongue pressure attached on the palate with denture adhesive (A) Swallow scan system (B) Location of sensors [START_REF] Hori | Newly developed sensor sheet for measuring tongue pressure during swallowing[END_REF] 2.2.2.3 Palatal plates with embedded pressure sensors [START_REF] Hewitt | Standardized instrument for lingual pressure measurement[END_REF] developed the Madison Oral Strengthening Therapeutic (MOST) that consisted of adult-sized polymer athletic mouth guard in which the palatal plate was made custom fit with use of dental putty and embedded with a conductive elastomer strain gauge sensor (Figure 8). Pressure readings were recorded by connecting the MOST mouthpieces to a simple electronic circuit. The average maximum isometric tongue pressure recorded for healthy subjects were 40 to 85 kPa. The pressure during swallowing of 10 ml of water ranged 13.05 to 289.75 kPa. Air bulbs have been shown to provide reliable measures of tongue pressure during swallowing, however it is definitely not suited for speech production because of two reasons;

(1) the bulbs are aligned on a straight strip that only enables the measure of pressure in the mid-sagittal plane of the palate. Whereas it can be argued that this location is relevant for the main tongue-palate interactions in swallowing, it is definitely not suited for speech production, in which lateral contacts are very important, in particular for the precise control of the central air channel that largely determines the characteristics of the consonantal acoustic sources [START_REF] Narayanan | An articulatory study of fricative consonants using magnetic resonance imaging[END_REF]; (2) the position of bulbs are difficult to adjust as it slides easily on tongue surface and the connecting tube which has to be held in position by subject biting on it thus perturbing the articulation.

Sensor sheet systems have been designed more recently, in the aim to minimize their impact on the geometry of the vocal tract i.e. thin (less than 1 mm) sensor sheets.

However, calibration issues have been raised in general for the sensor sheets. [START_REF] Hori | Newly developed sensor sheet for measuring tongue pressure during swallowing[END_REF] have shown, that the pressure measured with their resistive sensor sheet was almost twice smaller than the pressure measured with conventional pressure sensors, but with a good linear relation between both measures. Tiede et al., 2003 observed pervasive noise and inconsistencies in repeated measurements during speech production with a capacitive sensor sheet. Also, to date sensor sheets have not been extensively tested to be considered to be as reliable as well-established strain gauge sensors. In addition, since the sheets are pre-fabricated, independently of the subjects, and directly attached on the palate or on the plate, it is difficult to measure the pressure at the points that are the most relevant ones for each task and each subject.

Palatal plates with embedded strain gauge sensors have the advantage of measuring tongue pressure during both swallowing and articulation, as they allow the subject to close his/her mouth and perform the functions. Also, strain gauge sensors are reliable with a good stability in time and in temperature. However, the palatal plates have to be thick enough (i.e. a few mm) to include the sensors and the wires. The thickness is a drawback for reliable in vivo measurements, because it perturbs the usual speech or swallowing movements with some clear impacts on the pressure [START_REF] Kieser | Measuring intraoral pressure: adaptation of a dental appliance allows measurement during function[END_REF].

Hence it requires to include an acclimatization period in the experimental protocol, which is not compatible with the usual duration of an experiment.

In an overall view, most of the devices are capable of measuring tongue pressure in either speech production or swallowing. However, palatal plates embedded with pressure sensors are efficient to measure tongue pressure during both functions, as they allow the subject to close his/her mouth. Therefore, we have developed our system that relies on the old principle of a palatal plate with embedded strain gauge sensors, but to innovate by using it with specific subjects, namely complete edentulous subjects, who have been wearing their complete denture for months and got used to speak and swallow with it, without being perturbed. The strain gauge sensors are inserted into a duplicate of the complete denture, in order to not induce any perturbation to the usual speech and swallowing motor strategies of the subject. The advantages are that we can rely on the excellent properties of the strain gauge sensors, without requiring any acclimatization period from the subjects. In addition, our approach is intrinsically suited for the study of subject-specific characteristics, since the device is specifically designed for each subject, with sensor locations chosen to reflect the main articulatory characteristics of the subject. Since the original work done with [START_REF] Jeannin | PRESLA: An original device to measure the mechanical interaction between tongue and teeth or palate during speech production[END_REF] we have significantly improved the sensors, which are now build up in a private company that is specialized in the design of electronic chips and sensors. We also tremendously improved the electronics for the measure, in order to have a high signal-to-noise ratio. These improvements were brought to the device in order to reach a very good description of the variation of the pressure over time, in the frequency range [0-30Hz] which is usually used in the collection of jaw, tongue or lip movements in speech production.

MATERIALS AND METHODS

The originality of our project is to exploit an experimental device that has been developed in Gipsa-Lab that measures not only the location of the contacts between the tongue and prosthesis but also the mechanical characteristics of these contacts. This device, is called PRESLA and it allows the precise measurements of the mechanical pressures exerted by the tongue on the prosthesis plate and their temporal evolution [START_REF] Jeannin | Tongue pressure recordings during speech using complete denture[END_REF]. The which is a strain transducer device for measuring geometrical change on the surface of a mechanical structure. Measurement of strain has applications in measuring force, pressure, acceleration and torque. Strain gauge is composed of a steel cantilever beam mounted on insulating flexible backing. This gauge is attached to the object with suitable adhesive. When a force is applied, the object is deformed, the foil is deformed. This change causes change in its electric resistance. The variation of the resistance is small and its measure requires a specific electrical circuit, called Wheatstone bridge (Hoffmann, 1989) (Figure.11). Although theoretically, any metal conduction can be used as a gauge, the metal requires certain characteristics: exceptionally small size and mass, simplicity to be attached to the deformable object; accurate response in equilibrium with changes in the fixed surface; no interference with the stiffness and other characteristics of the object over which it is mounted; high sensitivity in the direction of measured strain and low sensitivity in the transverse plane; quick response and negligible time lag; insensitiveness to ambient conditions such as temperature, humidity, vibration; inexpensive, reliable and readily available. 1976) and modified by [START_REF] Jeannin | Tongue pressure recordings during speech using complete denture[END_REF] This choice is justified by the compromise between the capacity of this sensor to be used in biologic environment (safety measures, biocompatibility), and the characteristics of its design (cost, availability) and its mechanical performance, which includes mechanical resistance, thermal stability, resistance to corrosion, sensitivity, range of measurement and simplicity to use. Last but not the least, the most crucial factor is the adaptability of the sensor. The sensor can be adapted to meet the demands for precise experimentation, in our case the measure of the tongue-palate pressure. The sensor had been previously used for measurement of lip articulation force [START_REF] Garnier | Efforts and coordination in the production of bilabial consonants[END_REF]) by gluing the sensor on lower lip. The sensor consists of 13 layers with each layer contributing to its mechanical performance (Figure .12). The sensor is composed of a cantilever stainless steel beam, 0.1 mm thick, in the middle layer. On either side of this beam are bonded two strain gauges (Vishay, ref EA06 062 AQ 350). The water proofing is done with help of three protective films of dental varnish (Copalite®). The technical details of the sensor are presented in the table 1. Transverse sensitivity (+0.9 ± 0.2) % Table 1. Technical details of the sensors

ELECTRONIC PRESSURE MEASURING DEVICE

The measure of the pressure is made by measuring the change in the impedance of the strain gauge reflecting its strain under the influence of the pressure. This is done using a Wheatstone Bridge, which is included in a device that we call "Amplifier". The original PRESLA system consisted of analogic amplifier (Module 2160, Vishay Measurements Group) for the signal.

The analogic amplifier had low signal to noise ratio (Figure .13) and this affected the quality of signal measurements for both calibration and experiment. Another disadvantage of original analogic amplifier is that it could only support two sensors at one time. For detailed tempospatial measurement a device which can support at least 6-7 sensors at same time is needed so this analogic amplifier was not feasible for our goals. A new low-noise multi-channel amplifier has been specifically designed by Julien Minet (Gipsa-lab) in the context of this thesis, in order to improve the quality of the measure. This amplifier has 8 independent channels inputs, which can be connected to eight separate transducers. Each of the inputs is connected to a very low noise electric circuit including a Wheatstone bridge, which can be automatically balanced before each measure. The output of each measure circuit is proportional to the transducer's impedance, and hence to the mechanical pressure applied to it. All the 8 outputs are systematically sampled at 4 kHz in an interlacing manner. Software enables via USB interface to set up the gain of the outputs, to select the outputs for which the data are to be stored in the computer (see below). This results in signals which present clear improvement of the SNR, as compared to the former analogic amplifier (see Figure 13). In addition, electrical safety has been increased using only electronically components that don't use more than 9V which is the tension beyond which there is a danger to patients. Moreover, the electrical insulation of polarized sensors up to 30V has been successfully tested during electrical safety experiments.

materials and methods

-25 -| P a g e

Complete denture/prosthesis

According to Glossary of Prosthodontics [START_REF] Dentistry | The Glossary of Prosthodontic Terms Seventh Edition (GPT-7)[END_REF], complete denture is defined as 'a fixed or removable dental prosthesis that replaces the entire dentition and associated structures of the maxillae or mandible'.

DUPLICATE DENTURE MOUNTED WITH SENSORS

For our experiments a duplicate denture is fabricated from the patient's original prosthesis.

A duplicate denture is defined as 'a second denture intended to be a replica of the first'. The other synonyms for duplicate denture include copy denture, replica denture, template denture and repeated denture [START_REF] Dentistry | The Glossary of Prosthodontic Terms Seventh Edition (GPT-7)[END_REF]. The locations of sensors in the duplicate denture are chosen considering both speech and swallowing tasks. For this our preference is to equal number of sensors on central and lateral region as we believe palatal contacts are essentially central for swallowing but can be central and lateral for speech, depending on the location and the sound pronounced. The locations of the contacts differ across consonant and are determined by a palatogram done specifically for each sound. A palatogram is defined 'a graphic representation of the area of the palate contacted by the tongue during a specified activity, usually speech [START_REF] Dentistry | The Glossary of Prosthodontic Terms Seventh Edition (GPT-7)[END_REF]. Some examples of palatograms, for /t/ in logatome /ita/ and for /k/ in logatome/ika/ are shown in Figure .14. It is based on the technique that denture is sprayed with green coloured liquid which is obtained by mixing edible food colours. Green colour is specifically chosen as it imparts visually appreciable contrast against pink coloured denture base. The denture is then inserted in patient's mouth and correctly seated, taking appropriate caution that nothing comes in contact with the sprayed palate, before the sound was pronounced. Palatogram of a sound is generated by the action of tongue, wiping away the sprayed color film, forming definite patterns during speech task [START_REF] Farley | Palatogram assessment of maxillary complete dentures[END_REF]. Patient is asked to repeat the desired sound twice in a consecutive manner, during which definite palatal contact is confirmed by close observation. Patient is then instructed to avoid any further tongue contact to the palate. Denture is carefully retrieved without perturbing the obtained palatal record. The thin transducers (1 mm) and wires can be easily inserted into the palatal surface of denture (2-2.5 mm thick) without any change in its morphology. Small holes had to be cut on the palatal plate to accommodate the transducers (Figure 15). The transducer is held in place with plastic coat on its both sides (but not the sensing surface). One piece has been adhered to superior surface of palatal plate spanning the hole on the underside of transducer, a second piece covered the body of transducer except the sensing surface. The transducer sensing surface flushes with the palatal surface. Therefore, when the tongue contacts the active surface, the tongue/palate stress can be measured from the strain produced in the gauge. The wires exit from the vestibular side by the way of labial commissures and they are connected to the amplifier. An example of duplicate denture with six sensors mounted is shown in Figure 16. The literature shows a large variability in the pressure values of the tongue pressure along with different systems of measurements. The variability of pressure values has been shown in state of art chapter; ranging from 0.8 kPa during swallowing [START_REF] Hori | Coordination of tongue pressure and jaw movement in mastication[END_REF] to 289.75 kPa during swallowing [START_REF] Kieser | Measuring intraoral pressure: adaptation of a dental appliance allows measurement during function[END_REF]. A part of this variability may be associated with the method of the calibration of transducers. For this reason, it was logical to develop a calibration system adapted to measure the tongue pressure. PRESLA system was thus developed in 2007 at Gipsa-Lab as part of Jeannin's thesis. It is based on the concept of water column exerting a perfectly controlled pressure on the transducer via a finger latex. Hence the name 'Dried Water Column' was used. The Figure .17 shows what the original calibration of the PRESLA system looked like.

Description of components

a. The base and the swivel vise

The base consists of a stainless-steel system composed to sliding parts. These parts are screwed onto the cradle, it allows the user to move the parts within a 15cm range in the two dimensions in the horizontal plane. Its jaws are covered with rubber which allows to hold the prosthesis without risk of fracture. The jaws can be tilted and rotated 360 degrees.

b. Water column and Latex

The calibration procedure is based on the use of a water column, which is made of two plastic rigid tubes connected by a 3mm diameter soft pipe. The height of the water column can be adjusted by moving up and down the upper rigid tube (A1). The pressure in the water column is applied to the sensor via an extensible latex finger mounted on the lower tip of the lower rigid tube (A2). The height of the water column is marked by a millimeter scale. The angle between the tip of the latex finger and the sensor to be calibrated should be a right angle.

Drawbacks of the original calibration system

The original PRESLA calibration system had some drawbacks which were brought to notice and improvements were done in the context of this thesis, which will be discussed later.

The upper water column has to be moved up and down manually during calibration, which was not easy and could induce some inaccuracy in the pressure measurement. Also, it raised technical difficulties and prolonged experiment duration as calibration is done by single person and attention is shared on many aspects like computer screen ensuring proper recording, contact between finger latex and sensor ensuring proper contact, noting down the height of water level after every increase or decrease.

New Calibration Setup

Calibration procedure

For calibration the sensors are mounted on the prosthesis, in order to have conditions similar to those of the experiment. The prosthesis is firmly mounted on a fixed base (Figure 19, Panel A), in order to strictly prevent displacements under the effect of the pressure. The fixed base can be oriented specifically for the calibration of each sensor in the prosthesis.

Before calibration starts, the setup is arranged such that latex contacts with the transducer just slightly without pressure, the latex finger being essentially vertical and surface of the sensor in the prosthesis essentially horizontal (Figure 19, Panel A). This configuration is considered to determine the reference water height and reference electrical current in the sensors associated with a zero pressure on the sensor. Water height is controlled very precisely with a syringe connected to the latex finger via a soft tube, which is moved. The height of the syringe is precisely measured owing to the rotation of an electrical motor, after calibration, and it is shown on a digital display with accuracy below 1mm. The electrical current informing about the strain gauge sensor strain, and then the mechanical pressure, is digitized at rate of 4 kHz with constant amplifier gain setting and was displayed on a laptop using MATLAB and Signal Processing Toolbox Release 2015b.

Panel B of Figure 19 illustrates the result of such a calibration for a transducer. It shows the linear behavior of the transducer in the range of 0 to 5 kPa (i.e. 500 mmH20). A linear regression will used to model the relationship between the mechanical pressure and the intensity of the current with 'y axis' representing the pressure level (in mmH20) and 'x axis'

representing the output voltage. We assume that the observed linear behavior applies over a larger domain.

Labelling of Phonemes

The following acoustic events we plan to label using PRAAT (Figure 20) are:

• Onset and offset of consonant For instance, in [s] a jet of air is blown through a constriction in the alveolar part of the vocal tract, which generates vortices in the airflow; this turbulent airflow hits the upper incisors teeth, which results in strong high intensity and high frequency (above 5kHz) noise [START_REF] Shadle | Articulatory-acoustic relationships in fricative consonants[END_REF].

The Acoustics of Fricative Consonants. Unpublished Doctoral Dissertation. Cambridge, MA, Massachusetts Institute of Technology). In wide-band spectrograms, noise can be recognized by a structure that is quasi continuous along the time and the frequency axis, whereas voiced sounds are associated with a structure which is periodic in time and localized in the frequency band below 5kHz. In this section the events which has been labelled as in Figure 20 are introduced. Voice onset time (VOT) has been defined for stop consonants [START_REF] Lisker | A cross-language study of voicing in initial stops: Acoustical measurements[END_REF] as the duration between the moment of the release of the stop (acoustically marked by a noise burst)

and the onset of glottal vibrations and then voicing (acoustically marked by the onset of a periodic time pattern). When the stop consonant is released prior to voicing onset, the VOT is considered to be positive, while voicing onset that precedes the release is associated with negative VOT. In French, the unvoiced stops /p, t, k/ are known to be associated with positive VOT, and the voiced stops /b, d, g/ correspond to negative VOT values (refer to the Figure 21).

In our study we defined VOT-Lisker as the interval separating at the onset of the noise and the first oscillation of the periodic pattern after the noise onset. A slightly different duration related to the emergence of the vowel production after the consonantal release has been defined by Personal data will be entered into an excel file, at one time. This will be a simple entry. The experimental data will be acquired and stored in sound files (.wav type) and MATLAB data files (. mat type) or in video files (.avi type). This data will be stored temporarily on the computer used during the experiment and then, permanently and protected from outside access, in the lab backup system. Specific directories will be assigned to two cohorts of subjects. In the cohort 2 group, subdirectories will be defined that will contain the data collected in each session. The experimental data files will be named in accordance with the usual practices:

• Cohort 2:
o speech_number of subject_date of experiment_session o swallowing_number of subject_date of experiment_session The resulting measurement data on pressure signal will be measured and calculated using dedicated MATLAB program which we have developed specifically for this work; to extract the different variables that we will describe below. The variables measured on the acoustic speech signal will be extracted using the PRAAT software and MATLAB program that has been written to extract the spectral properties of the consonants. These data are automatically stored at the output of the program in excel files which will be used as input for the statistical processing performed with R software (URL http://www.R-project.org/). Some of the MATLAB programs written are described below. The calibration of sensor is the first step followed by the experiment and analysis.

For calibration of sensor

Only one sensor is calibrated at a time. The procedure starts with an automatic balance of the Wheatstone bridge of the selected channel, which includes a phase of 1 minute (offset)

necessary for the automatic setting to 0 of the sensors. Once the bridge is balanced, the calibration procedure itself can start. The MATLAB program enables to control the gain (which is kept constant), duration of calibration and enables saving of data with name and session (Figure 22). The output voltage is recorded over a duration of 300 seconds (5mins) during which the height of the water column is progressively increased, step-by step with the increment of 5 cm till the height of 50-60 cms.

For recording of tongue pressure during experiment

The procedure starts with a balance of the Wheatstone bridge of all the channels by progressively reducing the output voltage of the bridges to 0 over a total duration of 180 seconds, which has been proved to be sufficient to reach a true balance for each channel. After

For analyzing the pressure patterns

The program is used to label the pressure signals and to measure the pressure at specific times (figure below). It enables to display the pressure signals in synchrony with the speech signal. The acoustic events, which have been labelled with PRAAT beforehand, are displayed in order to help select the time intervals of interest for the pressure analysis. The figure 24 shows an example of this command on pressure data of water swallow. The pressure signals are displayed in kPa thanks to the sensor specific linear regression inferred from the calibration.

It also enables to identify each acoustic event in order to know its onset and offset for example each consonant or each swallow. An example of data from sensor 5 for /ita/ is shown below.

Experimental protocol

The ultimate goal of the research project to which this PhD work is related, is a clinical study of patients with complete maxillary dentures. The goal is to measure the spatial-temporal distribution of the pressure exerted by the tongue at different points of the prosthesis during speech tasks (focus on consonants that require palatal contacts) and swallowing tasks (dry/water). In speech tasks the acoustic signal will also be analyzed and the spectral properties of the consonants will be measured.

Two populations will be considered separately: (1) a population of patients used to their prosthesis, whom we consider to be fully adapted to it for speech and swallowing; (2) a population of patients who just received their prosthesis, and have to progressively adapt to it for speech and swallowing. The first population will be used to establish a reference database about the tongue palate interactions during speech and swallowing under normal condition.

The second population will be used in a longitudinal study in order to investigate the process of adaptation to the prosthesis.

Depending on the population, we will carry out two types of statistical analyses. On the one hand for patients used to their prosthesis, descriptive statistics will be used to describe the links between mechanical pressure at different points of the prosthesis and the properties of speech or swallowing under conditions that we considered to be normal. On the other hand, inferential statistics (Generalized Linear Models) will be used to characterize the process of adaptation in new patients over time and compare their performance to the population of patients used to their prosthesis.

Target Populations

This study focuses on complete edentulous subjects with complete maxillary prosthesis. This study involves two cohorts of patients.

Exclusion criteria

Volunteers with speech, language disorders

Volunteers with neurological or psychological disorders

Volunteers having complains about the performance of the complete dentures in respect to retention and stability

Minor volunteers and pregnant women

Volunteers who have declined to participate at any stage of the study

Discomfort felt by volunteers during experiment

Experimental tasks

Maximal tongue function

The maximum tongue function is an important parameter to account for intrinsic individual characteristics as it gives information about the subject specific tongue muscles' strength, via their global capacity to exert pressure on the palate.

Anterior isometric tongue endurance: Each subject has to "push the tip of tongue as hard as possible against the anterior sensor for as long as they can". The maximal pressure is recorded as well as the total duration of the pressure plateau during each trial.

Anterior isometric tongue strength: Each subject has to "push the tip of tongue as hard as possible against the anterior sensor for 3 seconds". The maximum pressure is recorder for each trial.

Posterior isometric tongue endurance: Each subject has to push the blade of tongue as hard as possible against the posterior sensor for as long as they can". The maximal pressure is recorded as well as the total duration of the pressure plateau during each trial.

Posterior isometric tongue strength: Each subject has to "push the blade of tongue as hard as possible against the posterior sensor for 3 seconds". The maximum pressure is recorder for each trial.

Swallowing task

During the swallowing tasks the same recording will be done as in the speech tasks, including the audio signal. This audio signal informs about the occurrence of the beep that the subject is asked to press when he/she swallows. In addition to this beep acoustic signal, in order to detect the time interval during which the subject swallow, a video recording of the neck and mouth region, which does not disclose the identity of the subject (Figure 25). This video will show the laryngeal (hyoid) movement, which will enable us to find correlation between tongue pressure production and laryngeal movement during bolus intake.

Dry swallow

The subject is instructed to normally swallow his/her own saliva. The subject reports the swallowing by pressing the beep.

Water swallow

The subject is instructed to drink 10ml of water. The subject reports the swallowing by pressing the beep. [ʒ]The subjects will be given a binder containing 5 sheets.

On each sheet would be written in large and clear font three lists made of the 16 logatomes arranged in different random order;

[ita] [ati] [ida] [adi] [ika] [aki] [iga] [agi] [isa] [asi] [iza] [azi] [iʃa] [aʃi] [iʒa] [aʒi]
. The patient would be instructed to read aloud and distinctly each list at normal speaking rate.

The actual recording time is estimated at 35 minutes. Each subject has his/her own duplicate which is stored in a separate box and cleaned after each use by suitable disinfectant wipes. The investigator is equipped with sterile latex gloves and has a mask and a gown.

Data collection: location of research

There are two locations of research and the following tasks are carried out; Our main objective is to exploit the data to infer the following;

1. In subjects adapted to their prosthesis: to propose a spatial-temporal reference description of the pressure distribution on the prosthesis during each consonant production and swallowing).

2. In the subjects new to their prosthesis: to study the change of the pressure signals with learning over time (longitudinal study) and the link with the improvements of the characteristics of the speech signal produced and the efficiency of swallowing.

3. In the subjects new to their prosthesis: to establish the links between these pressures, their amplitudes, their localizations, their temporal coordination, and the acoustic and temporal properties of the consonants for the task of speech, or the quality of the swallowing.

4. We would like to evaluate the tongue motor biomechanics during swallowing for both required tasks (dry and water swallow) which would be new kind of new information.

Labelling of the acoustic signal of speech during the production of an unvoiced consonant will allow us to measure the onset and offset of the noise (Ton-noise and Toff-noise), the interval separating Ton-noise and the onset of the resumption of the vibration of vocal folds (TVOT-Lisker)

and finally the interval separating the Ton-noise and the onset of post-consonantal laminar airflow (TVOT-Klatt). Similarly, the labelling of pressure signals on each sensor will allow us to identify, during the production of consonant or during swallowing, the onset and offset of positive pressure phase (Tonset and Toffset) and the time of maximum pressure (Tmax) and the amplitude of maximum pressure (Pmax).

For objective 1, we will analyze the acoustic properties of consonants (in the frequency and the time domains) and pressure patterns (temporal and amplitude) of swallowing on subjects who are well adapted to their prosthesis, to recognize those who would have difficulty in these tasks. Afterwards on the subjects not having difficulties, we will perform a descriptive analysis of the different temporal measurements and amplitude measurements on the pressure signals,

distinguishing between the different consonants and the two swallowing tasks.

For objective 2, the focus will be on subjects who are new users of prosthesis during their initial recording session, which we will compare to subjects adapted to their prosthesis and without any problems. We will perform on each pressure variable an inferential statistical analysis, separating speech production and swallowing, based on generalized linear models with mixed effects, in which the variable to be explained will be one of the variables measured, the fixed effects will be the session (1st session, 1 month, 3 months), the type of consonant or the swallowing task, the position of sensor (anterior to posterior and lateral to medial) and the repetition index (from 1 to 15), and the random effect will be subject.

On this basis we will measure for each sensor variables characterizing the signal specific to this sensor, variables characterizing the temporal co-ordination between the sensors. We will also measure variables characterizing the acoustic production of consonants.

RESULTS OF PILOT EXPERIMENT

In this chapter, I will provide examples of data collected during speech production and swallowing with our experimental methodology. Because we did not obtain on time the ethical approval (Comité de Protection des Personnes (CPP) application 69HCL18_0103) for the study that is described in the preceding chapter, these data are those of our last pilot experiment, which is the most recent and the most rigorous study that we have been able to run in the context of this thesis. Obviously, it is not possible to draw any general conclusion from such a limited amount of data, collected on a single subject. It was not possible to run any descriptive or inferential statistical analysis along the lines that we described above. However, these data, in particular the speech data, nicely illustrate the kind of investigation that is now possible thanks to the development and the refinement of our methodology. The data about time contact patterns during the production of stop consonant have been in large parts presented in a paper that is now published in the international peer-reviewed journal "Clinical Linguistics and

Phonetics" [START_REF] Mirchandani | Study of tongue-palate pressure patterns during the hold phase in the production of French denti-alveolar and velar stops[END_REF].

Experimental conditions for pilot study

In order to measure the mechanical pressure exerted by the tongue against the palate during speech production and swallowing tasks, we ran an experimental session with an edentulous patient, who is an old user of complete denture. This section is devoted to the presentation of experimental data collected on that subject and of their analysis, in order to illustrate the nature of the information that can be inferred thanks to our device.

THE SUBJECT

The subject was a male native speaker of French (age 54 years) with no self-reported history of speech, language or hearing impairments. He was completely edentulous and has been using a maxillary and mandibular complete denture for more than a year, which was well maintained by periodic inspection. Ahead of the experiment, the subject was assessed objectively for the range of movement of the lips, tongue and jaw and was confirmed to have no lingual or oral motor disorders. Informed consent was obtained after explaining the aim and methodology of the study.

EXPERIMENTAL SETUP

The maxillary denture worn by the subject was replicated to fabricate a duplicate For this subject, the speech production task consisted of lists of 8 logatomes arranged in different random order: /ita/ /ati/ /ida/ /adi/ /ika/ /aki/ /iga/ /agi/ /isa/ /asi/ /iza/ /azi/. The patient was instructed to read aloud and distinctly each list at normal speaking rate. During the recording, the patient was seated in a dental chair in upright position to allow reading of a corpus in comfortable amplitude and pitch. The microphone was placed at the distance of 10 cm. The acoustic signal obtained from the microphone was recorded with a professional portable audio and MIDI interface (M-Audio Fast Track Pro). The speech data were recorded at 22.05 kHz and displayed on a computer screen with Audacity® software. The data from the 6 strain gauge transducers were gathered simultaneously via the amplifier.

Before processing, the acoustic signal was undersampled at 16 kHz for further spectral analysis and labelling, and the pressure signals were undersampled at 300Hz and low-passed filtered at 30Hz with a linear phase FIR filter. A number of acoustic events were labelled on the acoustic signal as described in methodology section: the beginning and end of the consonant and its surrounding vowels; the beginning and end of the consonantal burst; the VOT-Lisker;

the VOT-Klatt. The low-passed filtered pressure signal recorded from each of the 6 sensors were labelled according to time events related to the consonant production as described in methodology section. The offset of the rising phase (trise) and onset of the decreasing phase (tdec) were determined using a threshold on the first derivative of the pressure signal, corresponding to 20% of the amplitude of the positive and negative velocity peaks respectively (see Figure 29). the horizontal lines above and below the x-axis respectively mark the 20% threshold of the positive velocity peak in the rising phase and the 20% threshold of the negative velocity peak in the decreasing phase; trise=Offset of rising phase; tdec=Onset of decreasing phase.

Denti-alveolar and velar stops analysis

With the recorded data, we wish to emphasize the questions that can be addressed with our experimental device, because of the precise description of the time variation of the interaction between the tongue and the palate, in the phase during which there is very small amplitude of tongue movements which renders the use of traditional kinematic measures useless.

VIRTUAL TARGET HYPOTHESIS

In speech production the target control theory suggests that the central nervous system controls the movements of the vocal tract articulators by specifying discrete changes in their postures. According to this hypothesis, movement is generated to carry the motor system from an initial to an intended final posture, each of these postures being associated with a basic unit of speech, the phoneme. When the phoneme is a stop consonant (like /p,t,k,b,d,g/ in English), during which the tongue is in contact with palate in order to seal the vocal tract before the consonantal release, it has been hypothesized that the posture would correspond to a virtual tongue shape that would be higher than the palate. The distance between the intended and unreachable tongue shape would thus explain why the tongue exert a pressure on the palate.

This "virtual target hypothesis" was first proposed by [START_REF] Lofqvist | Lip and jaw kinematics in bilabial stop consonant production[END_REF] for labial stops suggesting that lower (or upper) lip moves towards a target located above (or below) the actual position of the upper (or lower) lip and contact happens between these targets which will not be reached. Löfqvist, (2000) also suggested that the virtual target hypothesis would enable the control the closure duration of the stop. It has also been shown to be very useful to interpret kinematic differences associated with voicing degrees in Korean stops [START_REF] Brunner | Adaptation strategies in perturbed/s[END_REF] During the consonantal closure, when the tongue is in contact with palate, it barely moves vertically because of the palate being an impassable obstacle. However, according to virtual target hypothesis tongue muscle activation continues to vary as it would do in the absence of palate to reach the virtual target. This results in an underlying virtual movement that is not cinematically observable because of the palate but dynamically measurable by the increase of the mechanical pressure exerted by the tongue on the palate. Figure 30 illustrates schematically this phenomenon from a kinematic perspective. Figure 30 and Figure 31 illustrate well the differences in tongue-to-palate pressure time variations depending on whether the tongue is controlled according to the "virtual target hypothesis" or as a ballistic movement. The Virtual Target Hypothesis results in a plateau in the time variation of the pressure, while the ballistic movement results in a bell-shaped pressure variation over time.

In order to assess this issue for each consonant separately over all the repetitions, independently of the variations in the duration and amplitude of the pressure, we have normalized for each consonant in a given vowel context the time variation of the pressure from its onset Tonset to its offset Toffset, in time (dividing the time by the duration (Tonset -Toffset)) and in amplitude (dividing the amplitudes by the maximum value). To provide a statistical description of this variation, we have plotted using ggplot2 package [START_REF] Team | R: a language and environment for statistical computing[END_REF] for each consonant in a given vowel context the 95% confidence interval and the prediction interval at one standard deviation of these normalized time patterns. The 95% confidence interval corresponds to the range of values in which the true value of the mean of the considered variable should be with a 0.95 probability. The prediction interval refers to a range of values that is likely to contain the value of the considered variable for any single new observation given the mean value and the standard-deviation computed from the available data. Hence the prediction interval reflects the uncertainty on the value of each single observation of the considered variable, while a confidence interval reflects the uncertainty around the mean value of the considered variable. Thus, a prediction interval at one standard-deviation is generally much wider than the 95% confidence interval.

We observed for this specific subject clear difference between the pressure patterns observed for /t/ and those observed for /k/ (Figures 32 and34). While the pressure patterns for /t/ are essentially bell-shaped, with the decreasing phase starting immediately after the end of the rising phase, the pressure patterns observed for /k/ show a plateau-like pattern. These observations suggest for our subject that for /t/, the underlying movement of the tongue tip, i.e.

the movement that would exist if the palate would not stop it, could be ballistic rather than directed toward a "virtual" target above the palate. In contrast, for /k/ the underlying movement of the tongue body seems to be directed toward a virtual target located above the palate, which is hold for a significant duration; this would explain the existence of a target pressure value around which the pressure barely varies during a significant duration. The difference is clearer and results are in expected direction for /ita/ and /ida/ versus /ika/ and /iga/ however the patterns results of pilot experiment -57 -| P a g e are quite similar for /ati/, /adi/, /aki/ and /agi/ as they are closer to asymmetrical bell-shaped patterns that to target-like patterns (Figures 33 and35). This could be due to fact that the tongue contact does not decrease as much for V2 = /i/ as they do for /a/. The second question is related to the difference between voiced and unvoiced consonants.

It has been suggested that unvoiced consonants could be associated with increased pressure of the tongue against the palate [START_REF] Dixit | Linguotectal contact patterns in the dental and retroflex stops of Hindi[END_REF][START_REF] Kochetov | Voicing and Tongue-Palate Contact Differences in Japanese Obstruents (< Feature Articles> Articulatory Phonetics: Focus on Japanese)[END_REF]. In order to enable a statistical evaluation of this question independently of the variations in the hold phase duration, we normalized in time the time variations of the pressure from its onset to its offset for each consonant in a given vowel context separately. We then plotted and compared the 95% confidence interval associated with each unvoiced stop and its voiced counterpart.

While clear differences in pressure amplitude are observed between /t/ and /d/ (Figure 36 and 37), the pressure measured for /k/ and /g/ look more similar (Figure 38), suggesting that the influence of voicing on tongue-palate interaction is variable according to the location of the occlusion in the vocal tract. The third question is regarding the relationship between the time variation of the pressure and the characteristics of the acoustic signal for unvoiced stops. For unvoiced stops, the increasing phase when tongue moves upward is important to ensure a rapid sealing of the vocal tract and generate an increase of the intraoral pressure that contributes to stop vocal fold vibrations and is required for the consonantal burst to be produced. The decreasing phase could be also very important for the production of the burst, since the tongue has to withdraw from the palate, in order to ensure the rapid opening of the vocal tract required for the burst production. In order to evaluate the time control of these phases we measured the duration of the increasing pressure phase Durincreasing (trise-Tonset) (see Figure .29) and the duration T2noise that separates the onset of the decreasing phase from the onset of the noise (tdec-Tnoise) (see Figure .29). Since we look for possible regularity in these durations, we considered for each unvoiced consonant their statistical distribution: small distributions provide evidence for regularities and possible precise control of these durations.

Figures 39 and40 show for /t/ and /k/, in all their repetitions, the distributions of the duration of the rising phase durrise and of the duration t2noise separating the onset of the descending phase to the onset of the burst, respectively. We observe that for both consonants the distributions of the duration of the rising phase are very narrow, around 30ms for /k/ and 40ms for /t/, in spite of the differences observed above in the normalized time pressure patterns. This suggests that in our subject this phase which is important for the sealing of the vocal tract, is precisely controlled and similarly for the denti-alveolar and the velar unvoiced stops. In contrast, the onset of the descending phase does not seem to be tightly controlled in relation to the onset of the burst, since for both stops the distributions of t2noise are large. It suggests that this onset does not play a major role in the production of the burst.

Analysis of fricatives

The alveolar fricatives /s/ and /z/ are known to have the same place of articulation [START_REF] Bauman-Wängler | Articulatory and phonological impairments: A clinical focus[END_REF]. The general description of /s/ and /z/ reports the existence of a "midline groove" required to preserve a narrow passageway for escaping air' [START_REF] Shriberg | Clinical phonetics[END_REF]. This narrow passageway is known to be a crucial feature for typical fricative production, as it allows channel of airstream to pass through thus creating the turbulent and fricative quality of these sounds [START_REF] Narayanan | An articulatory study of fricative consonants using magnetic resonance imaging[END_REF][START_REF] Shadle | Articulatory-acoustic relationships in fricative consonants[END_REF]). A typical EPG display showing the existence of this passageway for normal alveolar fricatives is given in Figure 41 [START_REF] Hardcastle | EPG-based description of apraxic speech errors[END_REF]: lateral contacts along the length of the palate are observed, which was termed lateral bracing, together with incomplete contact in the very anterior part of the alveolar ridge. This contact pattern is considered as a model for alveolar fricatives. Our first aim in this study of French fricatives in our pilot subject was get an idea of the time variation of the pressure during the control of the lateral grooving of the tongue. We expected the data to reveal a target-like pattern with no or small variation of the pressure on the lateral sensors and no or very little pressure on the sensors close to the mid-sagittal plane.

Consistent with our expectations, we found that sensors 5, 4 and 1, located close to the midsagittal plane (see Figure. Contrary to our expectations, our data do not provide any evidence supporting the hypothesis of a target-like control of the tongue during the grooving phase of the alveolar fricatives: a target-like pattern would show a quasi-constant pressure during a large part of the grooving phase; our data rather show, for the unvoiced /s/ and for the voiced /z/, bell-shaped time patterns of the pressure. The pressure patterns observed in the consonant when it precedes vowel /a/ are clearly bell-shaped; the patterns observed before vowel /i/ context are bell-shaped in their first part, but then they either remain on a plateau or increase again at the end of the grooving phase, probably as a results of an anticipation of the subsequent front and high vowel /i/. The observation of bell-shaped patterns at least in the first part of the production of the fricatives suggests that similar tongue control could underlie the production of alveolar stops and alveolar fricatives, namely a ballistic movement of large amplitude towards the palate.

These results are quite surprising. An alternative hypothesis could be that tongue muscles do provide a constant amount of force during the grooving phase, and that the pressure exerted against the palate would decrease as soon as the airflow passes through the narrow channel between the tongue and the palate, and pushes the tongue apart from the palate. This The second aim of our study was to investigate the difference between voiced and unvoiced fricatives. It has been suggested with EPG data that there is significantly more alveolar tonguepalate contact for voiced /z/ than for voiceless /s/ in word-initial position [START_REF] Dagenais | A study of voicing and context effects upon consonant linguapalatal contact patterns[END_REF][START_REF] Mcleod | Tongue/palate contact for the production of/s/and/z[END_REF]. In order to enable a statistical evaluation of this question, we normalized in time the time variations of the pressure from its onset to its offset for each consonant in a given vowel context separately. We then plotted and compared the 95% confidence interval associated with voiced /z/ and unvoiced /s/. The figure 44 show the 95% confidence interval of the pressure time patterns normalized in time and pressure for the alveolar fricatives (/s/ and /z/).

The pressure amplitude measured for voiced /z/ was minimally larger than for voiceless /s/.

This finding is not in agreement with conclusions of EPG studies of consonants in Consonant-Vowel-Consonant sequences [START_REF] Dagenais | A study of voicing and context effects upon consonant linguapalatal contact patterns[END_REF][START_REF] Mcleod | Tongue/palate contact for the production of/s/and/z[END_REF], in which it was suggested on the basis of the amount of alveolar EPG contacts that voiceless fricatives would involve a less strong mechanical interaction with the palate than their voiced counterpart.

TIME ORDERING OF PRESSURE PRODUCTION AT SENSORS

The time sequence showed coordination of tongue pressure from anterior to posterior (Figure.46). There was significant difference between onset of contact in anterior and posterior sensors and Tons was earlier in anterior sensors. There was difference between the duration of the increasing phase (Tons-Tmax) and decreasing phase (Tmax -Toff); the decreasing phase was significantly longer.

The durations used to characterize the time variations of tongue pressure measured at each sensor during swallowing (the time of Tons, Tmax and Toff, the interval among each time) are given in Figure 46 and Table 2 below. Tons at Ch 5 was set to 0, as it is located in the region of the palate where the first contacts should occur during swallowing. In agreement with data available in the literature [START_REF] Ono | Pattern of tongue pressure on hard palate during swallowing[END_REF] we observed an increase of the pressure time onset from the front to the back, within a range of 100ms in average (see Figure 46). However, the trial-to-trial variability of the data is surprisingly large (Table 2), so that our data did not reveal any statistically reliable difference across sensor location in the pressure time onset. This large variability was not expected, in particular because of the accuracy of the time variation of the pressure signals, which is make possible thanks to our low-noise new device.

CHARACTERISTICS OF PRESSURE PATTERN AMONG SENSORS

In order to assess the characteristics of the pressure variations over time for the water swallow event, we have normalized for each sensor in each swallow the time variation of the pressure from its onset Tons to its offset Toff, both in time (dividing the time by the whole duration (Tons-Toff) and in amplitude (dividing the amplitudes by the maximum value measured during the contact interval). To provide a statistical description of this variation, we have plotted 1 for each swallow context the 95% confidence interval and the prediction interval at one standard deviation of these normalized time patterns at the three sites (anterior, middle and posterior).

We observe for the three sensors located in or close to the mid-sagittal plane (Ch 5,4, and 1) (Refer Left panel of Figures 45,46,47) pressure time patterns that are in agreement with data of the literature: in average the pressure measured on these sensors is strong immediately after the onset and decreases afterwards. For the sensors located aside the mid-sagittal plane (Ch 2, 3, and 6) the patterns are variable, from a clear asymmetric profile for Channel 6 to a plateau-like profile for Channel 2 (Refer Right panel of Figures 45,46,47) . We did not expect such a large variability, and further recordings seem to be required, in order to evaluate and understand this variability more properly. It is therefore clearly premature to make inferences regarding the clinical implications of these findings. Future research is needed to explore the possibility if complete denture users can experience challenges in generating tongue pressure patterns in a stable manner, either for dry or water swallow. In addition, studies in another cohort of population with new users of complete denture should explore the relationship between pressure pattern stability and swallowing control for improving the design of prosthesis.

Summary of results

In the design of our study protocol and experimental setup, we attempted to investigate tongue motor control when it is in contact with the palate and when, as a result, its movements are limited and strongly constrained by external factors. An original aspect of our experimental procedure is that we collect data from edentulous subjects who wear complete denture for more than a year. The advantage of this procedure is that our pressure sensing device does not perturb the articulation, since the subjects are used to speak with their denture and are beyond the adaptation phase. The disadvantage of this procedure is that it reduces the scope of our investigations to a specific population, in which adaptation to the denture can take different paths and induce different reorganisation of the motor control strategies. However, it is known that introducing in the oral cavity, objects that modify the palatal surface inevitably generates motor adaptation processes that are complex [START_REF] Honda | Compensatory responses of articulators to unexpected perturbation of the palate shape[END_REF][START_REF] Thibeault | Articulatory and acoustic adaptation to palatal perturbation[END_REF]. Hence, collecting data from subjects with normal conditions would not avoid the key-problem of the adaptation process. have shown that this process can span over at least two weeks. This makes the problem all the more complex, if one uses subjects who have to go through this adaptation process for the purpose of a study that does not investigate adaptation, but 'normal' speech production. An alternative solution could be to use much thinner capacitive pressure sensors [START_REF] Puers | Capacitive sensors: when and how to use them[END_REF]. However, it has been found that the calibration of this kind of sensors in the range of pressure associated with tonguepalate interaction is quite inaccurate.

In this context we consider that our experimental setup applied to edentulous subjects provides an interesting compromise to investigate with the required accuracy the time variation of the pressure exerted on the palate during speech production. Our calibration procedure based on a Dried Water Colum leads to pressure values that are in agreement with data published in the literature in the (1-20 kPa) range [START_REF] Wakumoto | A pressure sensitive palatography: Application of new pressure sensitive sheet for measuring tonguepalatal contact pressure[END_REF]. The sensitivity of the sensors and the low-noise amplifier allow accurate measure of the time variation of pressure.

With the data collected on a single subject, we have shown that the data are appropriate to tackle basic issues related to the control of the tongue during stop consonants: does the strategy used to achieve the contact with the palate correspond to a movement toward a virtual target above the palate or to a ballistic movement of large magnitude? Are voiced consonants produced with less force than their unvoiced counterparts? How does the control of the tongue be related to the acoustic cues of the consonants? Other issues that can be addressed in speech production are, the amount of interspeaker variability associated in particular with palatal shape, the influence of aging or neurological disorders on pressure strength, the asymmetry of the tongue-palate interaction, but also in swallowing since the time coordination of the contacts at different locations of the palate can be precisely described. It has also an obvious applicability in the investigation of speech disorders characterized with inaccurate tongue placement in the relation to the palate. Hence, we think that the original pressure sensing device that we presented in this paper opens doors for new investigations of tongue motor control in time intervals where tongue kinematics does not carry enough relevant information.

Most research measuring tongue pressure for swallowing only focuses on healthy dentulous subjects wearing palatal plate mounted with sensors, in our knowledge this study is first attempt to study the temporal relationship along tongue pressure in complete denture subject with 6 sensing points using new generation transducers [START_REF] Kaires | Palatal pressures of the tongue in phonetics and deglutition[END_REF]. Different researchers have developed devices to determine tongue pressure during swallowing. IOPI [START_REF] Robbins | Age effects on lingual pressure generation as a risk factor for dysphagia[END_REF] has shown favourable performance in large studies to investigate tongue strength and endurance due to its simplicity [START_REF] Adams | A systematic review and meta-analysis of measurements of tongue and hand strength and endurance using the Iowa Oral Performance Instrument (IOPI)[END_REF] however, it seems to be unsuitable for oral function assessment as it interferes with occlusion and has only one sensing point. Kay Pentax system consisting of air-filled bulbs based on the same principle and has more than one sensing point. Many researchers [START_REF] Ball | Comparison of two methods for measuring tongue pressure during swallowing in people with head and neck cancer[END_REF][START_REF] Hind | The effects of intraoral pressure sensors on normal young and old swallowing patterns[END_REF][START_REF] Steele | The influence of orolingual pressure on the timing of pharyngeal pressure events[END_REF] have used this device to measure tongue pressure during swallowing function, but it does not allow biting. On the other hand, there has been resurgence in interest regarding tongue-palate contact with pressure sensing instruments attached or mounted on an experimental palatal plate [START_REF] Kennedy | Tongue pressure patterns during water swallowing[END_REF][START_REF] Kieser | Measuring intraoral pressure: adaptation of a dental appliance allows measurement during function[END_REF]. The development of sensor sheet system that are attached to the palate enabled quantitative evaluation of tongue pressure [START_REF] Hori | Newly developed sensor sheet for measuring tongue pressure during swallowing[END_REF]. The device does not interfere with occlusion and have several sensing points [START_REF] Wakumoto | A pressure sensitive palatography: Application of new pressure sensitive sheet for measuring tonguepalatal contact pressure[END_REF]. This method has two disadvantages. First, the palate plate which can be at least 0.5 mm thick can interfere with articulation and needs adaptation period. The second disadvantage is that the sensor sheets can be difficult to sterilize and disinfect properly. Compared to other techniques our setup presents the advantages; the miniature sensors used in complete denture cause no change in geometry of oral cavity eliminating any interference with occlusion; the Dried Water Column provides a unique calibration of sensors which replicates characteristics of contact between soft body (tongue) and prosthesis; the specifications of new generation strain gauges provides quantitative measurements with high time accuracy.

The previous studies on dentate subjects demonstrated tongue contact against the hard palate starting from the anterior part to the posterior part during water swallow by studying the tongue pressure production (Takahiro [START_REF] Ono | Pattern of tongue pressure on hard palate during swallowing[END_REF]. From the preliminary result of one edentulous subject adapted to complete denture, the tongue pressure was initially generated in anterior region followed by middle region and the posterior region which is in agreement with results observed for dentate subjects. We also investigated the two patterns of tongue pressure by comparing the maximum amplitude and duration in monophasic and biphasic pattern. The duration in the monophasic pattern was shorter than biphasic. This similarities with previous results on healthy subjects [START_REF] Hori | Role of tongue pressure production in oropharyngeal swallow biomechanics[END_REF] are interesting and can be due to fact that the patient in this report is well adapted to his prosthesis.

In conclusion, despite the swallowing data showing huge variability and the difficulty we had to get regular signals the preliminary result showed the temporal coordination among tongue pressure. We have to think about a better protocol to impose more regularity in the motor actions. It is acknowledged by us that we will need few more pilot experiments to understand where the problem comes from.

DISCUSSION AND CONCLUSIONS

The first choice of prosthetic rehabilitation for the completely edentulous patients is with complete dentures. The McGill consensus on overdenture suggests that patients with conventional maxillary denture opposing an 2-implant mandibular overdenture should be the first choice treatment for completely edentulous population [START_REF] Thomason | Two implant retained overdentures--A review of the literature supporting the McGill and York consensus statements[END_REF]. With the ever-increasing number of edentate population and growing demand for prosthesis, there is rising responsibility placed on prosthodontists to provide adequate prosthetic treatment which will not only replace missing oral structures and preserve remaining tissues but also preserve the functional tasks carried out in the oral cavity such as mastication, swallowing and articulation of speech. Therefore, there is a need to focus on research to study the impact of design of complete dentures in relation to swallowing and speech production and its adaptation.

During oral phase of swallowing, when the bolus is prepared it is collected on the tongue and directed towards the oropharynx. The teeth come early in maximum intercuspation contacts, to stabilize the denture in its bearing surfaces by distributing harmoniously the occlusal contacts over the entire bearing surfaces. Thanks to these occlusal contacts in maximum intercuspation, the mandible becomes a support point to elevate the hyoid and triggering the transfer of bolus towards the stomach by peristaltic movements. This reference is utilized in for complete denture, wherein the potential movement of the mandible is balanced by slight moving of the prosthetic base on the bearing mucosa. This instability can decrease the functional efficiency of denture and also cause resorption of underlying supporting tissues [START_REF] Ellis | Conventional rehabilitation of edentulous patients: the impact on oral health-related quality of life and patient satisfaction[END_REF]. In the same way during speech production, the tongue contacts with the palatal plate in different manner depending on the character of speech sound that can influence the stability in a favourable manner or not. The optimization of the lingual and the palatal surface is thus important to improve the retention and stability of denture.

Knowledge of the distribution of pressure developed in the context of swallowing is necessary to achieve this optimization We believe that the experimental results and the design of the experimental protocol that we provided in this thesis will help us in this regard because of three main assumptions; (1) the instability of complete denture is the main cause of the difficulties that denture users experience in speech production and swallowing tasks; (2) this instability is essentially related to the morphology of the false palate or palatal plate that is not specifically adapted to resist the mechanical pressures exerted by the tongue and the lips in these oral motor tasks;

(3) a precise knowledge of the spatial distribution of these mechanical pressures and their temporal coordination is the ideal way to explain the principles of denture design that are adapted to the motor control strategies and the morphological characteristics of each patient including those with structural or functional deficits which can be congenital or acquired to ensure the resistance to these pressures and therefore the ideal stability of the prosthesis.

When people transition from being dentate to edentulous, and then use complete dentures, additional functional needs are placed on tongue. In addition to involving in primary oral functions such as speech and swallowing, the tongue is required to provide assistance with denture retention and stability and for this reason tongue assistance with maxillary denture retention is listed as a criteria in the Functional Assessment of Dentures (FAD) [START_REF] Corrigan | The development of a method for functional assessment of dentures[END_REF]. However, the effect of tongue position on maxillary denture remains questionable [START_REF] Kotsiomiti | Factors related to the resting tongue position among partially and completely edentulous subjects[END_REF]. We choose six sensors to know precisely the symmetry of the tongue support and its behaviour during functions articulation and swallowing. There were many differences in the pattern of tongue-palate contact between swallowing and articulation, and these differences related to position of tongue pressure and biomechanical parameters. Using this temporal information, patient can be taught to position the tongue in purposeful manner to improve retention and stability of denture.

Constant repetition with use of coordinated exercises can help these patients learn muscular activity patterns to aid in retention and stability [START_REF] Brill | The role of learning in denture retention[END_REF]. For these reasons, the capability of our experimental device to record mechanical interactions at multiple sites of prosthesis is an important step towards the specification of general principles for the design of complete denture; to make most of the tongue support and facilitate the good quality of speech and swallowing. These goals if achieved will improve the comfort of edentulous patients Dysphagia (difficulty in swallowing) is an important issue in the elderly patients wearing complete dentures. These patients often have problems in bolus formation and transportation due to age-related decline of tongue movement [START_REF] Sonies | Tongue motion in elderly adults: Initial in situ observations[END_REF] and lower tongue muscular strength [START_REF] Robbins | Age effects on lingual pressure generation as a risk factor for dysphagia[END_REF]. Multipoint measurements of tongue pressure against the palate has enabled researchers detailed analysis of tongue movement during swallowing from biomechanical point of view, described by magnitude, duration and sequential coordination among points [START_REF] Hori | Newly developed sensor sheet for measuring tongue pressure during swallowing[END_REF][START_REF] Ono | Pattern of tongue pressure on hard palate during swallowing[END_REF]. In denture wearing and tongue cancer patients, pathological changes and loss of this coordination has been reported [START_REF] Kondoh | Effect of complete denture wearing on tongue motor biomechanics during swallowing in edentulous older adults[END_REF][START_REF] Ono | Clinical application of tongue pressure measurement during mastication and swallowing[END_REF]. We investigated these parameters on one edentulous subject adapted to his denture to characterize the tongue activity pattern by referring to data of tongue pressure measurements found in literature with healthy individuals (Takahiro [START_REF] Ono | Pattern of tongue pressure on hard palate during swallowing[END_REF]. The results suggested a temporal coordination among the sensors, there was decline in duration and amplitude of tongue pressure from anterior to posterior. Therefore, it clarified the normal functional characteristics of tongue movement by analysing order, duration of pressure and justifies our hypothesis of using cohort 1 as 'normal' subjects and using this reference to cohort 2 to understand tongue function during swallowing and how it is different in new users or patients with dysphagia. In order to study characterization of these mechanical interactions in normal speech production and swallowing, we have chosen group of edentulous subjects whom we consider to have adapted to their complete denture (cohort 1). In addition,

we chosen new users of complete denture (cohort 2), for a longitudinal study to observe the adaptation process of these subjects, and how it can lead to emergence of new motor control strategies. This design of the experimental protocol is an important part of this thesis that has been done that has established inclusion criteria, the motor tasks and the statistical method for the data analysis for this type of study.

Patients who has undergone resection of tongue or floor of mouth usually suffers from impairment of speech, mastication and swallowing due to restriction of tongue movement caused by structural loss or scar tissue [START_REF] Aramany | Prosthodontic rehabilitation for glossectomy patients[END_REF]. Articulatory behaviour after glossectomy has been studies using dynamic palatography (M. [START_REF] Wakumoto | Analysis of the articulation after glossectomy[END_REF][START_REF] Yoshioka | The pattern of tongue pressure against the palate during articulating glossal sounds in normal subjects and glossectomy patients[END_REF].. In glossectomy patients, the glossal sounds categorised into three types by type of articulation, stop plosive, affricate and fricative are often misheard due to improper or no contact of tongue with the palate. These sounds cannot be investigated by simply observing whether tongue contacts the palate or not. It is necessary to evaluate objectively the degree of tongue-palate contact to help in rehabilitation of these patients. Consonants are produced in different manner depending on place of articulation and manner of articulation Stop or oral occlusive is a consonant in which vocal tract is completely blocked so that all airflow ceases whereas fricatives are produced with partial occlusion with only narrowing of the vocal tract. We selected /t/ /d/, a stop plosive produced by instantaneous complete closure and release with the tongue blade. Therefore, the tongue needs to strongly contact and quickly move to articulate. We selected /s/ /z/, a fricative produced by forcing air at high velocity through a narrow channel made by the blade and mid-portion of the tongue. The main feature of fricatives is the curling of tongue to direct the air over the edge of teeth. The results we obtained are consistent with those theories: /t/ had stronger value of maximum pressure when producing the complete closure and the shortest duration when producing instantaneous release and /s/ has lowest pressure to produce the constriction and longer duration in maintaining it (Figure 34,35 and 41). Our findings indicate that both the factors of quantity and time of pressure are firmly concerned with articulation of glossal sounds. Therefore, by characterizing the tongue motor patterns of normal subjects and glossectomy patients, our device also has potential to provide important insights for evaluating the tongue mobility of glossectomy patients. The high signal to noise ratio amplifier which has is important part of this thesis allows us to limit the filtering of pressure signals to as low as 0-30 Hz. This makes it possible to study precisely the characterisation of pressure peaks. The results we obtained to assess the target-directed movement of tongue for which /t/ and /k/ showed pressure patterns of essentially bell and plateau like shape respectively, will help us to formulate a hypothesis on the nature of the brain motor controls involved in the tested task. We believe that, a continuous acceleration of the tongue pressure at the time of contact with the palate will allow to formulate the hypothesis of a target directed movement beyond the palate and therefore the implication of low-level brain motor control system. On the contrary, if the acceleration decreases around the palate, the hypothesis of a target directed movement by the tongue can be formulated and therefore the implication of high-level brain motor control system. This information is very important for the rehabilitation of patients who have suffered loss of lingual substance, mainly in case of oral carcinomas. Indeed, the nature of the brain motor control system involved will determine the mode of rehabilitation of the patient. In the case of high-level cortical motor control, this will be a relearning, whereas in the case of lowlevel motor control, it will be a matter of making an obstacle that tongue will come up against.

Therefore, by evaluating quantitatively the linguo-palatal contacts can present us will variety of applications such as designing reconstructive flaps and glossal prosthesis in these patients.

In that sense, our experimental setup is capable to serve as both diagnostic and therapeutic tool.

Therefore, to finally conclude, this thesis resulted in; collected on a single subject. Therefore, it was not possible to run any descriptive or inferential statistical analysis along the lines that was described in protocol 5. With longitudinal study our setup will be capable to serve as both diagnostic & therapeutic tool

(

  Figure.1. The types of devices available to study and measure tongue-palate contact pressure during speech production and swallowing.

Figure. 2 .

 2 Figure.2. EPG setup consisting of display, processing unit and artificial plate (Top). EPG plate (bottom left) and tongue-palate contact patterns observed in normal English-speakers during different consonants (bottom right). Picture from http://www.rosemedical.com/electropalatography.html.

Figure. 3 .

 3 Figure.3. Top Left: Schematic diagram of Robin's device. Top Right: IOPI (Iowa OralPerformance Instrument)[START_REF] Robin | System and method for detecting pressure of selected body parts[END_REF] https://iopimedical.com. Bottom: Lingual force transducer used by Bu Sha. The tip of the tongue is against the balloon (1),[START_REF] Sha | Force production of the genioglossus as a function of muscle length in normal humans[END_REF]

Figure. 4 .

 4 Figure.4. Kay Swallowing air-filled bulb array[START_REF] Ball | Comparison of two methods for measuring tongue pressure during swallowing in people with head and neck cancer[END_REF]

Figure. 5 .

 5 Figure.5. Disposable oral probe. Small inflated balloon (A), a plastic pipe as a connector (B),

Figure. 8

 8 Figure.8. (A) MOST I and (B) MOST II mouthpieces are shown, along with the (C) MOST I mouthpiece and electrical circuit[START_REF] Hewitt | Standardized instrument for lingual pressure measurement[END_REF]

Figure. 9 .

 9 Figure.9. Top panel: Location of pressure sensors and a constructed plate(Hori et al., 2006a).Bottom panel: Design of metal palatal appliance and positioning of the eight miniature pressure transducers[START_REF] Kieser | Measuring intraoral pressure: adaptation of a dental appliance allows measurement during function[END_REF]

Figure. 10 .

 10 Figure.10. Picture of the wireless device consisting of tongue pressure sensor enclosed in a biocompatible plastic support and placed on a maxilla model

  experimental setup is constituted of the following a. Pressure sensors/transducers (Strain gauge sensors) b. Complete denture or Prosthesis/Duplicate embedded with sensors c. Calibration device d. Measuring/Analyzing tools 3.1 Pressure sensors: strain gauges transducers 3.1.1 HISTORY AND PRINCIPLES OF STRAIN GAUGES Arthur C. Ruge and Edward E. Simmons invented in 1938 the concept of strain gauge,

Figure

  Figure.11. Working concept of resistance type strain gauge

Figure. 12 .

 12 Figure.12. Description of sensor (Left), Photo of sensor used (Right).

Figure. 13 .

 13 Figure.13. Low signal to noise ratio of the analogic amplifier (top left) versus high signal to noise ratio of the digital amplifier (top right). 8-channel Amplifier (bottom)

Figure. 14 .

 14 Figure.14. Palatogram of complete denture for /ita/ (Left) and /ika/ (Right). Definite contacts are marked with *

Figure. 15 .

 15 Figure.15. Small hole cut to accommodate the sensor.

Figure. 16 .

 16 Figure.16. Experimental denture with six sensors mounted

Figure

  Figure.17. Original PRESLA system (Left). Schematic diagram of calibration device (Right)

A

  new calibration setup was designed. A schematic diagram of it is shown in Figure.18. It consists of vertical measuring rods, which are two meters in height, with electric pulley motor on top for moving the water column. The two rods parallel to each other are square shaped, hollow and made up of stainless steel. The rods are supported by a strong wooden base whichkeeps the setup stable. The main component is the electric motor which is attached to a pulley regulated by a control box that also provides a digital display of the height in millimeters of the water column. Thus, the speed of the displacement of the upper tube of the water columns can vary from less that 1mm/sec to a few cm/s, which enables an accurate step-by-step positioning and a rapid resetting of the water height if necessary.

Figure. 18 .

 18 Figure.18. New experimental setup for the calibration (Left), Control box with display (Right top). The three buttons on display serves for different purposes; red button is for adjusting the '0' after setting the sensor and finger latex the upper water column is moved in such a way that upper level of water is at its level and then this distance is saved as '0'. The steel color switch indicates the direction of pulley movement with up and down direction. The yellow knob controls the speed of pulley movement. The base and swivel vise (Right bottom) showing the tube in relation to sensor.

Figure. 19 .

 19 Figure.19. Position of finger latex with respect to transducer during calibration (Top). Calibration of one transducer showing its linear behavior and results of the linear regression

•

  Onset and offset of consonantal noise • Onset and offset of Lisker Voice onset time (VOT-Lisker) • Onset and offset of Klatt Voice onset time To label the speech signal we have used both the time representation and the corresponding time-frequency representation called "spectrogram". A spectrogram results from the computation of Short Time Fourier Transform over a sliding time-window of signal (with a 3ms duration in our case, resulting in a so-called "wide-band" spectrogram). In a spectrogram, time is represented on the x-axis and frequency on the y-axis. Spectral intensity (i.e. amplitude of the Fourier Transform Module in dB) is depicted by the relative darkness of the representation. In wide-band spectrograms, the frequency intervals with high energy correspond to the darker band. They are associated with formants. A formant is a frequency around which a high acoustic energy exists in the speech wave. Each formant corresponds to an acoustic resonance in the vocal tract. For speech perception the most informative formants are the first three, appropriately referred to as F1, F2, and F3. Noise is a random signal, and in speech production it results from a turbulent airflow due to a strong constriction in the vocal tract (friction) or a complete closure of the vocal tract (occlusion) followed by rapid aperture.

Figure. 20 .

 20 Figure.20. Phonetic labelling of consonant /t/ in /ita/ on PRAAT. Legends; 1: Preceding vowel (/i/); 2: Duration of the consonant; 3: Subsequent vowel (/a/); 4: Boundaries of the consonantal noise; 5: Boundaries of Lisker Voice Onset Time (VOT-Lisker); 6: Boundaries of Klatt Voice Onset Time (VOT-Klatt).

  [START_REF] Stevens | Role of formant transitions in the voiced-voiceless distinction for stops[END_REF]. Role of formant transitions in the voiced-voiceless distinction for stops. We call it "VOT-Klatt". It was defined as the interval separating the beginning of noise from the onset of a clear formant structure in the spectrogram, which marks the resumption of laminar flow of air in the vocal tract.

Figure. 21 .

 21 Figure.21. Examples of VOT-Lisker in voiced (top panel), unvoiced (middle panel) and aspirated (bottom panel) stops in Thai. From[START_REF] Lisker | A cross-language study of voicing in initial stops: Acoustical measurements[END_REF]

Figure. 22 .

 22 Figure.22. User Interface to set-up the parameters of the MATLAB program for calibration.

  having disabled the automatic balance of the bridges the output voltages of the selected channel are recorded over time slots of 60 seconds during which the subject achieves the required speech or swallowing task. The Wheatstone bridge is rapidly balanced between each of these materials and methods -38 -| P a g e 60s time slots during the whole experiment. It is possible to record up to 8 eight sensors simultaneously. The program enables to save the recording as MATLAB file (Figure. 23).

Figure. 23 .

 23 Figure.23. User Interface to set-up the parameters of the MATLAB program used for recording tongue pressure during experiment.

Figure. 24

 24 Figure.24. A display of program for measurement of tongue pressure during /ita/. On the top panel is audio signal. Thanks to the program it is possible to zoom on a specific time interval, for all the channels in synchrony, and to play the corresponding speech sound. The vertical colored lines represent the acoustic events (magenta = onset of consonant, blue = onset of noise, green = offset of VOT-Lisker, yellow = offset of consonant and offset VOT-Klatt). On the bottom panel is the matching pressure signal for one of the channel. Thanks to the program it is possible to measure pressure peaks and valley. The green curve running parallel to pressure signal denotes its first derivative.

Cohort 1 :

 1 Volunteers with complete denture for at least 12 months Cohort 2: Volunteers who are new users of denture Inclusion criteria Bimaxillary completely edentulous volunteers of both sexes, over 18 years of age Native speakers of French, without known speech or hearing disorders, except the potential influence of the full denture materials and methods -41 -| P a g e Volunteers must accept to sign the informed consent prior to any study-related procedure Volunteers should have undergone a pre-inclusion medical examination by the coordinating investigator or one of the physicians associated with the study Volunteers of the cohort 1 should be satisfied with their denture in respect to retention and stability.

Figure. 25 .

 25 Figure.25. Subject during swallowing session.

Faculty

  of dental treatment at Hospital Civil of Lyon o Selection and recruitment of volunteers o Recordings of palatograms o Experimental recording of speech and swallowing data on volunteers Gipsa-Lab, UGA o Calibration of sensors o Placing sensors in the duplicate o Analysis of the data Expectation from measured variables

  denture of biocompatible resin (Triad, VLC denture base material, DENTSPLY International Inc, U.S.A) by a professional lab technician. The duplicate denture preserved the vertical dimension, occlusal plane, teeth position and denture base thickness (2-2.5 mm) of the original one. In order to measure the mechanical pressure exerted by the tongue against the palate, six transducers were affixed on the prosthesis. The location of the transducers was chosen as for to cover the range of variation in contact location on the palate during the speech production and swallowing. The palatal plate if divided into parts; medial and lateral; anterior, middle and posterior (Refer to Figure26). The transducers were placed at antero-medial (Ch.5), anterolateral (Ch.3), middle-medial (Ch.4), middle-lateral (Ch.6), posterior-medial (Ch.1) and posterior-lateral (Ch.2) positions (Refer to the Figure27). The schematic diagram of setup has been shown in Figure28.

Figure. 26 .

 26 Figure.26. Picture giving information about how the regions for placing the sensors were determined[START_REF] Mirchandani | Study of tongue-palate pressure patterns during the hold phase in the production of French denti-alveolar and velar stops[END_REF]

Figure. 29 .

 29 Figure.29. Segmentation and labelling of the pressure signals. Panel a: Time variations of the pressure signal (in kPa, dark solid line) and its first derivative (light solid lines) during the production of /t/ in /ita/, as detected on the audio signal; the vertical lines show from the left to the right the beginning of the consonantal hold phase, the onset of the burst, tnoise, and the offset of the burst, labelled with PRAAT ; ton=Onset of positive pressure phase; toff=Offset of positive pressure phase. Panel b: Zoom on the time variation of the pressure signal in the interval [ton, toff] as shown in Panel a. are considered for the segmentation of the positive

Figure. 30 .

 30 Figure.30. Illustration of the virtual target hypothesis in the case of the production of an [ata] sequence. Left Top Panel: Vocal tract configuration in the mid-sagittal plane for [a] (assumed for sake of simplicity to be the same for both [a]); front is on the left. Middle Top Panel: Vocal tract configuration in the mid-sagittal plane for [t] (solid line) superimposed to the [a] configuration. Right Top Panel: schematic but realistic trajectory (red line) of a flash point on the tongue tip during the production of [ata]; the tongue does not go higher that the boundary defined by the palate. Lower Panel: illustration of the virtual trajectory (dotted blue line) toward the virtual target (schematized for the flesh point by the red circle) above the palatal boundary.The X-ray tracings are borrowed from Bothorel, A., Simon, P., Wioland, F., Zerling, J.P.

Figure 31

 31 Figure31illustrates the correlates in time of a virtual trajectory of the tongue above the palatal boundary, cinematically (in the vertical directions) and dynamically (tongue-to-palate pressure), in two cases: (1) the virtual trajectory is intended toward a virtual target and this target is hold during a certain duration (Top panels) is maintained at the virtual target during a certain duration; (2) the virtual trajectory results from a ballistic movement, that is not directed toward a target, which intended amplitude exceeds the palatal boundary (Bottom panels)

Figure. 32 .

 32 Figure.32. Pressure time patterns normalized in time and in amplitude. Dark grey shaded region: 95% confidence interval; light grey shaded region: prediction interval at one standard deviation. Top panel: /t/ in /ita/, Sensor 5 (left) and Sensor 6 (right). Bottom panel: /k/ in /ika/, Sensor 1 (left) and Sensor 2 (right).

Figure. 33 .

 33 Figure.33. Pressure time patterns normalized in time and in amplitude. Dark grey shaded region: 95% confidence interval; light grey shaded region: prediction interval at one standard deviation. Top panel: /d/ in /ida/, Sensor 5 (left) and Sensor 6 (right). Bottom panel: /g/ in /iga/, Sensor 1 (left) and Sensor 2 (right).

Figure. 34 .

 34 Figure.34. Pressure time patterns normalized in time and in amplitude. Dark grey shaded region: 95% confidence interval; light grey shaded region: prediction interval at one standard deviation. Top panel: /t/ in /ati/, Sensor 5 (left) and Sensor 6 (right). Bottom panel: /k/ in /aki/, Sensor 1 (left) and Sensor 2 (right).

Figure. 35 .

 35 Figure.35. Pressure time patterns normalized in time and in amplitude. Dark grey shaded region: 95% confidence interval; light grey shaded region: prediction interval at one standard deviation. Top panel: /d/ in /adi/, Sensor 5 (left) and Sensor 6 (right). Bottom panel: /g/ in /agi/, Sensor 1 (left) and Sensor 2 (right).

Figure. 36 .

 36 Figure.36. 95% confidence intervals of the pressure time patterns normalized in time for the voiced and unvoiced stops. Left panel: /t/ in /ita/ (black lines) versus /d/ in /ida/ (grey lines), sensor 5. Right panel: /t/ in /ita/ (black lines) versus /d/ in /ida/ (grey lines), sensor 6

Figure. 39 .

 39 Figure.39. Distribution of the rising durations for all the occurrences of /k/ (top panel) and /t/ (bottom panel)

Figure. 41 .

 41 Figure.41. Typical EPG display for alveolar fricatives. The black squares show where tongue contacted the palate (Front is on the Top, Back in the bottom)[START_REF] Hardcastle | EPG-based description of apraxic speech errors[END_REF].

  27) did not show any relevant positive pressure signal during the grooving phase, whereas the alveolar-lateral sensor 6 does show significant pressure variations during this phase. The figures 42 and 43 show the 95% confidence interval and the prediction interval at one standard deviation of the pressure variation measured over time on sensor 6, again normalized in time and in amplitude, respectively for /s/ /z/.

  phenomenon deserves further analysis to understand the underlying control mechanism: one of the possible paradigm in this regard would be to observe the pressure patterns for fricatives that are hold during a long and unusual time, and for increasing lung pressure, inducing increasing air pressure in the constriction area of the vocal tract and then potentially increasing passive downward displacement of the tongue, which would induce a reduction of the pressure against the palate.

Figure. 42 .

 42 Figure.42. Pressure time patterns normalized in time and in amplitude measured in the lateral part of the alveolar region with sensor 6. Dark grey shaded region: 95% confidence interval; light grey shaded region: prediction interval at one standard deviation. Left panel: /s/ in /isa/. Right panel: /z/ in /iza/.

Figure. 43 .

 43 Figure.43. Pressure time patterns normalized in time and in amplitude measured in the lateral part of the alveolar region with sensor 6. Dark grey shaded region: 95% confidence interval; light grey shaded region: prediction interval at one standard deviation. Left panel: /s/ in /asi/. Right panel: /z/ in /azi/.

Figure. 44 .

 44 Figure.44. 95% confidence intervals of the pressure time patterns normalized in time for the voiced and unvoiced fricatives. Left panel: /z/ in /iza/ (black lines) versus /s/ in /isa/ (grey lines), sensor 1. Right panel: /z/ in /azi/ (black lines) versus /s/ in /asi/ (grey lines), sensor 6

Figure. 45 .

 45 Figure.45. Example of time pressure pattern of swallowing event in one of the sensors Eighteen swallows were analysed.

Figure. 46 .

 46 Figure.46. The time course of tongue pressure produced at each sensor. Tons was set 0 sec at Ch 5 (see Table below for details, in particular related to the variability of the measures)

Figure. 47 .

 47 Figure.47. Pressure time patterns in the anterior part of the palate for water swallow normalized in time and in amplitude. Dark grey shaded region: 95% confidence interval; light grey shaded region: prediction interval at one standard deviation. Left panel: Sensor 5 (anterior-medial). Right panel: Sensor 3 (anterior-lateral)

1.

  Developed an experimental setup to record dynamic tongue-to-palate pressures during both speech and swallowing from multiple sites within the prosthesis without perturbation of vocal tract discussion and conclusions -80 -| P a g e 2. The preliminary data, nicely illustrate the kind of investigation that is now possible owing to the development and the refinement of our methodology & protocol 3. It opens doors for new investigations of tongue motor control in time intervals where tongue kinematics tools do not carry enough relevant information 4. It was not possible to draw any general conclusion from such a limited amount of data,

  versions ofUnix, Linux, Mac and Microsoft Windows (2000, XP, Vista, 7, 8, 10). The program supports speech synthesis, including articulatory synthesis. PRAAT is a very flexible tool to do speech analysis. It offers a wide range of standard and non-standard procedures to help in speech analysis, speech synthesis, learning algorithms, labelling and segmentation, speech manipulation, listening experiments, and more. For this study we use the 6.0.16 version of 2016.

	3.4.1 PRAAT

PRAAT is a free computer software package for the scientific analysis of speech in phonetics. It was designed, and continues to be developed, by Paul Boersma and David Weenink of the University of Amsterdam. It can run on a wide range of operating systems, including various

Table 2 .

 2 Mean values and Standard deviations of the durations characterizing the time variations of tongue pressure measured at each sensor during water swallow.

			17 ± 0.13	1.19 ± 0.35	0.17 ± 0.13	1.02 ± 0.35
	Ch 3	0.01 ± 0.008	0.15 ± 0.08	1.32 ± 0.45	0.14 ± 0.08	1.17 ± 0.41
	Ch 6	0.02 ± 0.005	0.23 ±0.09	1.14 ± 0.37	0.21 ±0.09	0.91 ± 0.37
	Ch 4	0.03 ± 0.004	0.16 ± 0.12	1.13 ± 0.37	0.13 ± 0.12	0.97 ± 0.40
	Ch 1	0.06 ± 0.009	0.17 ± 0.21	1.21 ± 0.42	0.11 ± 0.09	1.04 ± 0.38
	Ch 2	0.1 ± 0.006	0.29 ± 0.09	1.31 ± 0.41	0.20 ± 0.21	1.01 ± 0.38

Acknowledgements

Dear Reader, Welcome to my thesis. The present manuscript tells the context, the approach and the results associated with my three years of research carried about at GIPSA-Lab and LMI.

Sensors variable

Maximum

These three variables will be obviously only be used for study of speech production.