Neuromechanical Modelling of Articulatory Movements from Surface Electromyography and Speech Formants

Speech articulation is produced by the movements of muscles in the larynx, pharynx, mouth and face. Therefore speech shows acoustic features as formants which are directly related with neuromotor actions of these muscles. The first two formants are strongly related with jaw and tongue muscular activity. Speech can be used as a simple and ubiquitous signal, easy to record and process, either locally or on e-Health platforms. This fact may open a wide set of applications in the study of functional grading and monitoring neurodegenerative diseases. A relevant question, in this sense, is how far speech correlates and neuromotor actions are related. This preliminary study is intended to find answers to this question by using surface electromyographic recordings on the masseter and the acoustic kinematics related with the first formant. It is shown in the study that relevant correlations can be found among the surface electromyographic activity (dynamic muscle behavior) and the positions and first derivatives of the first formant (kinematic variables related to vertical velocity and acceleration of the joint jaw and tongue biomechanical system). As an application example, it is shown that the probability density function associated to these kinematic variables is more sensitive than classical features as Vowel Space Area (VSA) or Formant Centralization Ratio (FCR) in characterizing neuromotor degeneration in Parkinson's Disease.This work is being funded by Grants TEC2016-77791-C4-4-R from the Ministry of Economic Affairs and Competitiveness of Spain, Teka-Park 55 02 CENIE-0348_CIE_6_E POCTEP (InterReg Programme) and 16-30805A, SIX Research Center (CZ.1.05/2.1.00/03.0072), and LO1401 from the Czech Republic Government

A two-sling mechanism of hyolaryngeal elevation in the pharyngeal phase of swallowing

Thesis (Ph.D.)--Boston UniversityThe pharyngeal phase of swallowing is a complex function that transfers a bolus from the oral cavity through the hypopharynx into the esophagus. A critical event in this process is the elevation of the hyolaryngeal complex, which opens the upper esophageal sphincter and relocates the airway away from an oncoming bolus. The suprahyoid group of muscles (mylohyoid, geniohyoid, digastric, and stylohyoid) and thyrohyoid are thought to underlie this function. The role of a deeper posterior sling of muscles that is comprised of stylopharyngeus, salpingopharyngeus and palatopharyngeus has not been determined. This project aims to investigate a hypothesized two-sling mechanism for hyolaryngeal elevation in the pharyngeal phase of swallowing. The thesis begins with background information of the functional anatomy thought to underlie hyolaryngeal elevation followed by an outline of studies that validate the structure, function, and clinical relevance of the two-sling mechanism. A cadaver model is first used to calculate potential force vectors of the muscular slings. The function of the two-sling apparatus is then investigated in vivo by using muscle functional MRI to evaluate muscles active in swallowing and dynamic MRI to perform kinematic analysis on key anatomical landmarks that represent attachment sites of the two-sling mechanism. Finally, the clinical significance of the two-sling mechanism is demonstrated by comparing spatial and temporal measurements collected from fluoroscopic imaging studies of patients with normal swallowing ability and swallowing difficulty

Alterations in rhythmic licking behaviors following fibrosis in the rat mylohyoid muscle.

Muscle injury is a common side effect of radiation treatment for head and neck cancer. To increase understanding of muscle injury related dysfunction, we investigated the effects of oral swallowing function after cryoinjury to mylohyoid muscle in rats. The hypothesis is that injury to the mylohyoid delays the temporal licking pattern, resulting in aberrant drinking behaviors. Six rats received bilateral mylohyoid injuries by applying a 3mm cryoprobe. Licking behavior was measured by electrophysiological recordings of rhythmic tongue movements in a ten-minute drinking session taken pre-and post-injury (one-and two-weeks). Lick frequency and total licks per cluster decreased significantly one-and two-weeks post-injury compared to pre-injury (both p\u3c 0.03). Cluster size also significantly reduced (p\u3c 0.05) and the number of clusters performed increased post-injury (p= 0.002). Results demonstrate that injury to the mylohyoid muscle leads to aperiodicity of licking behaviors likely attributed to delays in tongue motility

The avian lingual and laryngeal apparatus within the context of the head and jaw apparatus, with comparisons to the mammalian condition: Functional morphology and biomechanics of evaporative cooling, feeding, drinking, and vocalization

© Springer International Publishing AG 2017. All rights reserved. The lingual and laryngeal apparatus are the mobile and active organs within the oral cavity, which serves as a gateway to the respiratory and alimentary systems in terrestrial vertebrates. Both organs play multiple roles in alimentation and vocalization besides respiration, but their structures and functions differ fundamentally in birds and mammals, just as the skull and jaws differ fundamentally in these two vertebrate classes. Furthermore, the movements of the lingual and laryngeal apparatus are interdependent with each other and with themovements of the jaw apparatus in complex and littleunderstood ways. Therefore, rather than updating the existing numerous reviews of the diversity in lingual morphology of birds, this chapter will concentrate on the functionalmorphological interdependences and interactions of the lingual and laryngeal apparatus with each other and with the skull and jaw apparatus. It Will

A computational neuromuscular model of the human upper airway with application to the study of obstructive sleep apnoea

Includes bibliographical references.Numerous challenges are faced in investigations aimed at developing a better understanding of the pathophysiology of obstructive sleep apnoea. The anatomy of the tongue and other upper airway tissues, and the ability to model their behaviour, is central to such investigations. In this thesis, details of the construction and development of a three-dimensional finite element model of soft tissues of the human upper airway, as well as a simplified fluid model of the airway, are provided. The anatomical data was obtained from the Visible Human Project, and its underlying micro-histological data describing tongue musculature were also extracted from the same source and incorporated into the model. An overview of the mathematical models used to describe tissue behaviour, both at a macro- and microscopic level, is given. Hyperelastic constitutive models were used to describe the material behaviour, and material incompressibility was accounted for. An active Hill three-element muscle model was used to represent the muscular tissue of the tongue. The neural stimulus for each muscle group to a priori unknown external forces was determined through the use of a genetic algorithm-based neural control model. The fundamental behaviour of the tongue under gravitational and breathing-induced loading is investigated. The response of the various muscles of the tongue to the complex loading developed during breathing is determined, with a particular focus being placed to that of the genioglossus. It is demonstrated that, when a time-dependent loading is applied to the tongue, the neural model is able to control the position of the tongue and produce a physiologically realistic response for the genioglossus. A comparison is then made to the response determined under quasi-static conditions using the pressure distribution extracted from computational fluid-dynamics results. An analytical model describing the time-dependent response of the components of the tongue musculature most active during oral breathing is developed and validated. It is then modified to simulate the activity of the tongue during sleep and under conditions relating to various possible neural and physiological pathologies. The retroglossal movement of the tongue resulting from the pathologies is quantified and their role in the potential to induce airway collapse is discussed

Biomechanical Models of Human Upper and Tracheal Airway Functionality

The respiratory tract, in other words, the airway, is the primary airflow path for several physiological activities such as coughing, breathing, and sneezing. Diseases can impact airway functionality through various means including cancer of the head and neck, Neurological disorders such as Parkinson\u27s disease, and sleep disorders and all of which are considered in this study. In this dissertation, numerical modeling techniques were used to simulate three distinct airway diseases: a weak cough leading to aspiration, upper airway patency in obstructive sleep apnea, and tongue cancer in swallow disorders. The work described in this dissertation, therefore, divided into three biomechanical models, of which fluid and particulate dynamics model of cough is the first. Cough is an airway protective mechanism, which results from a coordinated series of respiratory, laryngeal, and pharyngeal muscle activity. Patients with diminished upper airway protection often exhibit cough impairment resulting in aspiration pneumonia. Computational Fluid Dynamics (CFD) technique was used to simulate airflow and penetrant behavior in the airway geometry reconstructed from Computed Tomography (CT) images acquired from participants. The second study describes Obstructive Sleep Apnea (OSA) and the effects of dilator muscular activation on the human retro-lingual airway in OSA. Computations were performed for the inspiration stage of the breathing cycle, utilizing a fluid-structure interaction (FSI) method to couple structural deformation with airflow dynamics. The spatiotemporal deformation of the structures surrounding the airway wall was predicted and found to be in general agreement with observed changes in luminal opening and the distribution of airflow from upright to supine posture. The third study describes the effects of cancer of the tongue base on tongue motion during swallow. A three-dimensional biomechanical model was developed and used to calculate the spatiotemporal deformation of the tongue under a sequence of movements which simulate the oral stage of swallow

STANDARDIZED ELECTROMYOGRAPHIC ANALYSIS OF SWALLOWING AND CLINICAL APPLICATIONS.

BACKGROUND AND AIMS. Swallowing is a complex function which needs coordination between all the structures involved. To date a non-invasive method for the instrumental evaluation of oro-pharyngeal phase of swallowing is lacking. The aims of this study were: phase 1) to develop an electromyographical (EMG) protocol for the assessment of submental muscles (SM), to demonstrate its repeatability and to apply it to maximal voluntary clench (MVC), to quantify the relative contribution of SM; phase 2) to electromyographically analyse the oropharyngeal phase of swallowing finding a standardized and repeatable protocol, to find the physiological muscular pattern involved and to draw the standard model. MATERIALS AND METHODS. In 20 healthy subjects, aged 19-35 years, surface electromyography of SM, masseter (MM) and anterior temporalis (TA) muscles was performed; for phase 1, during maximal voluntary clenching (MVC) with and without cotton rolls and the pushing of the tongue against the palate, while for phase 2 during swallowing. Clenching on cotton rolls and pushing the tongue against the palate were used to standardise respectively MM and TA, and SM muscular potentials. Both phases were repeated in two appointments (T1-T2); submental muscles standardisation (during phase 1) and swallowing (during phase 2) were also repeated twice (A-B) in each session to assess repeatability. RESULTS. Phase 1: symmetry and activity were calculated for each couple of muscles. A two-way analysis of variance was computed for SM: no Factor 1 (T1 vs T2) or Factor 2 (A vs B) or F1 X F2 significant effects were found. SM recruitment was 31% of the maximal activity, with symmetry values larger than 80%. Phase 2: symmetry, activity and duration of activation for each couple of muscles were detected. In addition the duration of the whole exercise and the time of the maximal spike of activation for each muscle were evaluated. A two-way analysis of variance similar to the one of phase 1 was computed : no Factor 1 (T1 vs T2) or Factor 2 (A vs B) or F1 X F2 significant effects were found. Symmetry values were close to 80% for all the muscles, recruitment values were between 22 and 28% of the maximal activity for all the muscles with differences between all the muscles (the MM were the less recruited, while the TA were the most activated). Also the duration of activation of each couple of muscles resulted to be different between all the couples, the MM showed the shortest activation (an average value of approximately 1 s), while the submental muscles the longest one (an average value of more than 1.5 s). The duration of the whole swallowing was found to be between 1.5 and 2 s. Finally, the results showed that all the couples of muscles had their spike of activation between 35.87 and 42.65% of their total duration of activation. The sEMG graphic assessment of the position of the spike was reliable (two-way analysis of variance). CONCLUSIONS. The protocol demonstrated a high repeatability of the EMG indexes both intra and inter-appointment for MVC. Regarding swallowing it is reported that the protocol was repeatable for all the analysed indexes, although an high inter-individual variability. These results are probably due to the existence of different physiological models of swallowing among healthy population

The role of the primary motor cortex (M1) in volitional and reflexive pharyngeal swallowing.

Background and aims: The primary motor cortex (M1) controls voluntary motor behaviours. M1 has been identified to play a major role in the execution of voluntary corticospinal tasks as well as self-initiated corticobulbar tasks. However, the involvement of M1 in more complex corticubulbar tasks, such as swallowing, is not yet fully understood. Swallowing is quite different from other voluntary motor tasks as it has both voluntary and reflexive components. The degree of M1 involvement in the pharyngeal, or more reflexive, component of swallowing is unclear. Studies investigating the role of M1 in swallowing have yielded contradictory findings regarding the specific functional contribution of M1 to swallowing. Therefore, further investigation is warranted to clarify the role of M1 in pharyngeal swallowing. Discrete saliva or water swallowing has been utilized in most studies investigating neurophysiology of swallowing in health and disease. However, individuals most frequently complete multiple, consecutive swallows during the ingestion of liquid. Biomechanical differences between discrete and continuous water swallows have been identified using videofluoroscopic swallowing study (VFSS). However, no studies have investigated the pharyngeal pressure differences between these two swallowing tasks. Additional insights into task differences may be revealed through evaluation of pharyngeal pressure utilizing pharyngeal manometry. This research programme sought to clarify the role of M1 in reflexively and volitionally initiated pharyngeal swallowing. In order to understand M1 involvement in the execution of swallowing, comparative tasks that require known dependence on M1 were also included in this research programme. This research programme addressed the biomechanical changes in motor behaviours as a result of neural disruption during the performance of a number of motor tasks. This neural disruption was intrinsically generated through application of dual task (DT) paradigm and extrinsically generated using single pulse transcranial magnetic stimulation (TMS). A secondary aim of this research programme was to identify the differences in pharyngeal pressure generation between discrete and continuous swallowing. Methods: Twenty-four right handed participants (12 males, average age= 24.4, SD= 6.3) were recruited to this research programme. A number of motor tasks that vary in complexity were tested. These tasks included: volitional swallowing, reflexive swallowing, eyebrow movement, jaw movement and finger tapping with right, left, or bilateral index fingers. Participants performed multiple trials of several tasks in each study. Repetitions of tasks during a single session may affect performance due to factors such as fatigue or practice. A baseline study was undertaken to determine within-participant variability of measures across repeated trials. Following the baseline study, the role of M1 in pharyngeal swallowing was investigated in two main studies in counter balanced order. The role of M1 in pharyngeal swallowing was evaluated by investigating swallowing parameters during neural disruption using a DT paradigm. Participants performed tasks in isolation (baseline) and with interference that consisted of pairing swallowing with comparative task that activates M1 (fingers tapping and eyebrow movement tasks). In the other study, single pulse TMS was utilized to create an electrophysiological disruption to the areas of M1 associated with muscular representation of a number of motor behaviours (swallowing tasks, jaw movement and fingers tapping tasks). Stimulation was provided to both hemispheres in random order to evaluate laterality effects. Swallowing parameters and the performance of the other motor tasks were evaluated when performed with and without electrophysiological disruption. Differences in pharyngeal pressure generation between discrete and continuous swallowing were investigated using pharyngeal manometry. Pharyngeal pressures were recorded at three locations: upper pharynx, mid-pharynx and upper esophageal sphincter (UES) during four swallowing types: discrete saliva swallowing, discrete 10 ml swallowing, volitional continuous swallowing, and reflexive continuous swallowing. The research paradigm used in this research programme identified the effect of experimental conditions on the rate and regularity of task performance. In addition, pharyngeal manometry was utilised to measure the effect of experimental conditions on the pattern of the pharyngeal pressure generation during swallowing. Within subject differences from baseline were identified by means of Repeated Measures Analyses of Variance (RM-ANOVA). Results: Initial analysis of the data revealed that repetition of tasks within a session did not affect the rate and regularity of voluntary corticospinal tasks, voluntary corticiobulbar tasks nor swallowing tasks. In addition, repeating the swallowing tasks during a session did not affect pharyngeal pressure as measured by pharyngeal manometry. When motor tasks were performed concurrently in the DT paradigm, rate and regularity of eyebrow movements were significantly decreased when paired with swallowing tasks, whereas rate and regularity of swallowing were significantly decreased when paired with left finger tapping, but not right finger tapping. However, there was no significant effect of any task on the pattern of pharyngeal pressure generation. Extrinsically generated disruption using TMS significantly reduced rate and regularity of finger tapping tasks and regularity of jaw movement and swallowing tasks. In addition, interruption of pharyngeal M1 during the volitional swallowing task produced significant increase in the duration but not the amplitude of the pharyngeal pressure. Pharyngeal pressure generation differed between swallowing types and boluses types, in that saliva swallowing produced longer pharyngeal pressure duration and lower nadir pressure than water swallows. Discrete water bolus swallowing produced longer UES opening compared to both saliva swallowing or continuous water swallowing. Conclusion: The results of this research programme provided valuable methodological information regarding the effect of trials on task performance as well as identifying pharyngeal pressure differences between discrete and continuous swallowing. In addition to the methodological contribution, this research programme expanded on previous knowledge of neural control of swallowing, in that it extended the findings regarding potential role of M1 in pharyngeal swallowing. Given the absent effect of task repetition on the performance of corticospinal and corticobulbar motor tasks, it is speculated that outcomes of research investigating the effect of experimental manipulation on motor tasks performance is due to the experimental tasks, rather than natural variance in the data. The effect of swallowing on the rate and regularity of eyebrow movement, when performed concurrently using DT paradigm, suggest bilateral functional overlapping to a significant degree between neural substrates that control swallowing and orofacial muscles. These results offer partial support of bilateral representation of swallowing in the cortex. In addition, results further revealed potential involvement of right M1 in the regulation of pharyngeal swallowing as evidenced by a disruptive effect of left finger tapping on the rate and regularity of swallowing. The results from the hemispheric TMS disruption study support the active involvement M1 in the execution of voluntary corticospinal and corticobulbar motor tasks. In addition, the current findings extended previous knowledge of neural control of pharyngeal swallowing by documenting the effect of neural disruption on the regularity and pharyngeal pressure measures during volitional and reflexive swallowing. The current programme documented potential role of M1 in the control of pharyngeal swallowing possibly by modulating the motor plan at the swallowing CPG in the brainstem. This project is the first to document pharyngeal pressure differences between discrete and continuous swallowing. These findings contribute valuable information to the swallowing literature as limited number of studies investigated the biomechanical differences between discrete and continuous liquid ingestion. This knowledge will assist clinicians and researchers in identifying the pharyngeal pressure differences between normal and abnormal swallowing in different swallowing types and ultimately guide their rehabilitation decisions. Data from this research programme will add to the existing knowledge of neurophysiology of swallowing, thereby facilitating understanding of swallowing pathophysiology which is crucial for appropriate management of swallowing disorders

Speculations About the Selective Basis for Modern Human Craniofacial Form

The last few decades have seen an explosion of knowledge about the time and place of origin of our species, Homo sapiens. New fossils, more sites, better dates, modern and fossil DNA, and scores of analyses have mostly disproved the multiregional model of human evolution. By and large, the evidence generally supports some version of the out-of-Africa model, according to which humans first evolved in Africa at least 200,000 years ago and then migrated to other parts of the world. Remaining debates about human origins primarily address if and how much hybridization occurred between modern humans and taxa of archaic Homo such as H. neanderthalensis.Anthropolog