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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Association between Laryngeal Airway Aperture and the Discharge Rates of Genioglossus Motor Units

LaCross, Amy, Watson, Peter J., Bailey, E. Fiona 25 January 2017 (has links)
We know very little about how muscles and motor units in one region of the upper airway are impacted by adjustments in an adjacent airway region. In this case, the focus is on regulation of the expiratory airstream by the larynx and how changes in laryngeal aperture impact muscle motor unit activities downstream in the pharynx. We selected sound production as a framework for study as it requires (i) sustained expiratory airflow, (ii) laryngeal airway regulation for production of whisper and voice, and (iii) pharyngeal airway regulation for production of different vowel sounds. We used these features as the means of manipulating expiratory airflow, pharyngeal, and laryngeal airway opening to compare the effect of each on the activation of genioglossus (GG) muscle motor units in the pharynx. We show that some GG muscle motor units (a) discharge stably on expiration associated with production of vowel sounds, (b) are exquisitely sensitive to subtle alterations in laryngeal airflow, and (c) discharge at higher firing rates in high flow vs. low flow conditions even when producing the same vowel sound. Our results reveal subtle changes in GG motor unit discharge rates that correlate with changes imposed at the larynx, and which may contribute to the regulation of the expiratory airstream.
2

Obesity effects on lung volume, transdiaphragmatic pressure, upper airway dilator and inspiratory pump muscle activity in obstructive sleep apnoea.

Stadler, Daniel Lajos January 2010 (has links)
Obstructive sleep apnoea (OSA) is a common respiratory disorder characterised by repetitive periods of upper airway (UA) collapse during sleep. OSA is more common in males and the obese but the reasons why remain poorly understood. Abdominal obesity, particularly common in males, is likely to indirectly modulate the amount of tension (tracheal traction) exerted on the UA by the trachea and other intrathoracic structures, potentially leading to increased UA collapsibility. Other factors such as lung volume changes with obesity, altered drive to UA muscles and exaggerated arousal responses are also likely to contribute to UA instability. An investigation of these potential contributing factors forms the basis of this thesis. In the first study, the effect of external abdominal compression on UA collapsibility during sleep was investigated in a group of obese male OSA patients. A large pneumatic cuff wrapped around the abdomen was inflated to increase intra-abdominal pressure, aiming to produce an upward force on the diaphragm, designed to reduce axial tension on the UA. Abdominal compression increased end-expiratory gastric (PGA) and end-expiratory transdiaphragmatic (PDI) pressure by ~50% and produced a significant rise in UA collapsibility compared to the cuff deflated condition. These data support that increased intra-abdominal pressure has a negative effect on UA function during sleep. This effect may help explain why obesity is the leading risk factor for OSA and why OSA affects men more than women, given that abdominal obesity is particularly common in obese males. In the second study, differences in minimum expiratory (tonic) diaphragm activity during wakefulness were compared between 8 obese OSA patients and 8 healthyweight controls. Changes in tonic diaphragm activity and lung volume following sleep onset were also compared between the two groups. There was no evidence of increased tonic diaphragmatic activity during wakefulness in obese OSA patients to support significant diaphragmatic compensation for abdominal compressive effects of obesity. There were small decrements in lung volume following sleep onset in both groups (<70 ml), with significantly greater lung volume and diaphragmatic EMG decrements when sleep onsets were immediately followed by respiratory events. While lung volume decrements at sleep onset were relatively small, this does not discount that UA function is not more sensitive to effects of reduced lung volume in obese OSA patients. To more closely investigate the potential interactive effects of obesity on physiological variables likely influencing UA function, the third study investigated the temporal relationships between a comprehensive range of relevant physiological variables leading into and following the termination of obstructive apnoeas during sleep in 6 obese OSA patients. Prior to UA obstruction, diaphragm and genioglossus muscle activity decreased, while UA resistance increased. Lung volume and end-expiratory PGA and end-expiratory PDI also fell during this period, consistent with diaphragm ascent. There was a substantial increase in ventilation, muscle activity and lung volume immediately following the termination of obstructive events. Respiratory events and arousals occurred in close temporal proximity prior to and following obstructive apnoeas, supporting that cyclical respiratory events and arousals may both help to perpetuate further events. The results from this study support that there is a ‘global’ loss in respiratory drive to UA dilator and pump muscles precipitating obstructive respiratory events. The associated decreases in UA dilator muscle activity and lung volume may therefore both contribute to the propensity for the UA to obstruct. In summary, increased intra-abdominal pressure was shown to negatively impact UA airway collapsibility during sleep. A decrease in lung volume at sleep onset and prior to UA obstruction further support that lung volume decrement, coincident with a decline in overall respiratory drive, potentially contributes to the propensity for airway obstruction. Further studies are needed to elucidate the relative contribution of relatively small changes in lung volume versus changes in respiratory and UA muscle activity per se on UA patency in OSA patients. / Thesis (Ph.D.) -- University of Adelaide, School of Medical Sciences, 2010
3

Decoding the Language of Hypoglossal Motor Control

Laine, Christopher January 2011 (has links)
To effect movement, the central nervous system must appropriately coordinate the activities of pools of motoneurons (MNs), the cells which control muscle fibers. Sources of neural drive are often distributed to many MNs of a pool, and thus can synchronize the activities of targeted MNs. In this thesis, synchronization among MNs is used to investigate the strength, temporal progression, and anatomical distribution of neural drive to the hypoglossal motor nucleus (HMN), which controls muscles of the tongue. The HMN is an ideal target for such an investigation because it processes a host of functionally diverse inputs, such as those related to breathing, speaking, and swallowing. Study 1 characterizes motor unit (MU) synchronization within and across bellies of the human genioglossus (GG) muscle when MUs are activated by cortical drive (during voluntary tongue protrusion) or by automatic, brainstem-mediated drive (during rest breathing). We show that voluntary tongue protrusion synchronizes MU spike timing and firing rates within but not across bellies of the GG, whereas during rest breathing, MU firing rates are moderately synchronized both within and across muscle bellies. Study 2 documents respiratory-related synchronization of MU activities in muscles of the tongue and respiratory pump using an anesthetized rat model. The results of this study indicate that upper airway and respiratory pump MN pools share a low frequency respiratory-related drive, but that higher frequency (>8 Hz) synchronization is strongest in MU pairs of the chest-wall. Finally, Study 3 examines the potential for GG multi-unit and single MU activities to be entrained by cortical input. We show that during voluntary tongue protrusion, cortical oscillations in the 15-40 Hz range weakly synchronize MU population activity, and that EEG oscillations in this range intermittently influence the spike timing of individual GG MUs. These studies are the first to characterize MU synchronization by different sources of neural input to the HMN and establish a broad foundation for further investigation of hypoglossal motor control.
4

State-dependent Versus Central Motor Effects of Ethanol on Breathing

Vecchio, Laura Marie 16 February 2010 (has links)
This thesis tested the hypothesis that ethanol suppresses respiratory muscle activity by effects at the central motor pool and/or by state-dependent regulation of motor activity via influences on sleep/arousal processes. Ten rats were implanted with electroencephalogram and neck electrodes to record sleep-wake states, and genioglossus and diaphragm electrodes for respiratory recordings. Studies were performed following intraperitoneal injection of ethanol (1.25g/kg) or vehicle. The effects on genioglossus activity of ethanol (0.025-1M) or vehicle applied directly to the hypoglossal motor nucleus were also determined in sixteen isoflurane-anaesthetized rats. The results of these studies suggest that ethanol at physiologically relevant concentrations promoted sleep, and altered electroencephalogram and postural motor activities indicative of a sedating effect. The lack of effect on genioglossus activity with ethanol applied directly to the hypoglossal motor pool suggests that the suppression observed with systemic administration may be mediated via effects on state-dependent processes rather than direct effects at the motor pool per se.
5

State-dependent Versus Central Motor Effects of Ethanol on Breathing

Vecchio, Laura Marie 16 February 2010 (has links)
This thesis tested the hypothesis that ethanol suppresses respiratory muscle activity by effects at the central motor pool and/or by state-dependent regulation of motor activity via influences on sleep/arousal processes. Ten rats were implanted with electroencephalogram and neck electrodes to record sleep-wake states, and genioglossus and diaphragm electrodes for respiratory recordings. Studies were performed following intraperitoneal injection of ethanol (1.25g/kg) or vehicle. The effects on genioglossus activity of ethanol (0.025-1M) or vehicle applied directly to the hypoglossal motor nucleus were also determined in sixteen isoflurane-anaesthetized rats. The results of these studies suggest that ethanol at physiologically relevant concentrations promoted sleep, and altered electroencephalogram and postural motor activities indicative of a sedating effect. The lack of effect on genioglossus activity with ethanol applied directly to the hypoglossal motor pool suggests that the suppression observed with systemic administration may be mediated via effects on state-dependent processes rather than direct effects at the motor pool per se.
6

Acute and Chronic Effects of Artificial Rearing on Rat Genioglossus Muscle

Moore, Wayne Allen, Jr. 01 January 2005 (has links)
In most mammals, nutritive suckling is critical during the early neonatal period. The genioglossus (GG) muscle in rat plays an important role in protruding the tongue for efficient suckling. The purpose of this study was to examine the contractile properties and myosin heavy chain (MHC) phenotype of the GG following an early period of artificial rearing, which reduced nutritive suckling. Beginning at three days of age Sprague-Dawley rats were fed via implanted gastric cannula until postnatal day 14 (P14). At P14, artificially reared (AR) rat pups were either placed with a lactating dam until the end of the weaning period and allowed to mature until postnatal day 42 (P42), or anesthetized and prepared for physiological experimentation. GG contractile properties at P14 and P42 in AR and dam reared (DR) rats were obtained with a force transducer and digital recording system through stimulation of the medial branch of the hypoglossal nerve. Following physiological experimentation, muscle samples were removed and stored for MHC analysis. Comparisons were made between AR and DR groups at P14 and P42. At P14 maximum tetanic tension and fatigue index were lower in the AR group than the DR group and no differences were found in MHC distribution. By day 42, AR rats had a higher fatigue index that DR rats and DR rats had a higher percentage of MHCIIa than AR rats. The artificial rearing technique employed in this study was adequate to produce chronic changes in fatigue resistance and MHC distribution in GG muscle. GG muscle of premature human infants requiring early artificial feedings may develop similar changes in their contractile characteristics and MHC phenotype.
7

Premotor Mechanisms for Orofacial Coordination

Stanek IV, Edward John January 2016 (has links)
<p>The mouth, throat, and face contain numerous muscles that participate in a large variety of orofacial behaviors. The jaw and tongue can move independently, and thus require a high degree of coordination among the muscles that move them to prevent self-injury. However, different orofacial behaviors require distinct patterns of coordination between these muscles. The method through which motor control circuitry might coordinate this activity has yet to be determined. Electrophysiological, immunohistochemical, and retrograde tracing studies have attempted to identify populations of premotor neurons which directly send information to orofacial motoneurons in an effort to identify sources of coordination. Yet these studies have not provided a complete picture of the population of neurons which monosynaptically connect to jaw and tongue motoneurons. Additionally, while many of these studies have suggested that premotor neurons projecting to multiple motor pools may play a role in coordination of orofacial muscles, no clear functional roles for these neurons in the coordination of natural orofacial movements has been identified.</p><p>In this dissertation, I took advantage of the recently developed monosynaptic rabies virus to trace the premotor circuits for the jaw-closing masseter muscle and tongue-protruding genioglossus muscle in the neonatal mouse, uncovering novel premotor inputs in the brainstem. Furthermore, these studies identified a set of neurons which form boutons onto motor neurons in multiple motor pools, providing a premotor substrate for orofacial coordination. I then combined a retrogradely traveling lentivirus with a split-intein mediated split-Cre recombinase system to isolate and manipulate a population of neurons which project to both left and right jaw-closing motor nuclei. I found that these bilaterally projecting neurons also innervate multiple other orofacial motor nuclei, premotor regions, and midbrain regions implicated in motor control. I anatomically and physiologically characterized these neurons and used optogenetic and chemicogenetic approaches to assess their role in natural jaw-closing behavior, specifically with reference to bilateral masseter muscle electromyogram (EMG) activity. These studies identified a population of bilaterally projecting neurons in the supratrigeminal nucleus as essential for maintenance of an appropriate level of masseter activation during natural chewing behavior in the freely moving mouse. Moreover, these studies uncovered two distinct roles of supratrigeminal bilaterally projecting neurons in bilaterally synchronized activation of masseter muscles, and active balancing of bilateral masseter muscle tone against an excitatory input. Together, these studies identify neurons which project to multiple motor nuclei as a mechanism by which the brain coordinates orofacial muscles during natural behavior.</p> / Dissertation
8

Relação entre a força de língua e a posição do hioide em crianças com SAOS / The relation between force of the tongue and the position of the hyoid with OSAS

Souza, Jaqueline Freitas de 08 November 2017 (has links)
Objetivo: O propósito deste estudo consiste em avaliar a relação entre Força de Língua e medidas do posicionamento do hioide em crianças com diagnóstico de SAOS. Casuística e Método: Foram selecionadas crianças entre 07 e 12 anos, de ambos os gêneros, com história de roncos, apneias noturnas e respiração bucal crônica. Todas as crianças tiveram SAOS confirmada pela presença dos sintomas e pela polissonografia e foram divididas em dois grupos: pré-operatório e pós-operatório (pacientes que tinham diagnóstico de SAOS antes da adenotonsilectomia, e foram reavaliados 12 meses depois. Ambos os grupos foram submetidos à avaliação de força de língua isométrica máxima (FLIM), aplicada na posição de ponta e dorso de língua, através do dinamômetro (kgf) e por meio da radiografia lateral foi realizada avaliação craniofacial e posicionamento do hioide. Resultados: Na regressão linear em pacientes pré- operatório a medida cefalometrica D vert. H apresentou forte e significativa (p= 0,0083) relação negativa com a força em ponta de língua. Já em dorso de língua antes da cirurgia não foi significativa, para nenhuma das variáveis. Nos pacientes pós-operatório a FLIM do dorso e ponta foram significativamente (p<0,0330 e p<0,0098 respectivamente) relacionadas à medida cefalométrica C3-H. A comparação de medidas cefalométricas entre os grupos pré e pósoperatórios e entre o subgrupo residual e curados, não tiveram diferença na altura do hioide (HYS, HYMP, D Vert.H) e na relação ântero-posterior do hioide (D Horiz.H, C3-H). Em relação a FLIM da musculatura extrínseca da língua ao se compararem a média e desvio padrão nos pacientes pré e pós-operatório, observou-se que houve diferença para as medidas de força de língua (p= 0,0016 para dorso e p=0,0041 para ponta) entre eles. Não houve diferença entre os sub-grupos residual e curados. Conclusão: No presente estudo podemos concluir que existe relação entre a força do musculo lingual e a posição do osso hiode em crianças com SAOS. Ou seja, aumento na força dos músculos dilatadores da faringe pode influenciar a altura do hioide em crianças com SAOS. / Objective: The purpose of this study is to assess the relation between Force of the Tongue and measures of hyoid\'s positioning in children diagnosed with OSAS. Casuistry and Method: Were selected children between 07 and 12 years, from both genders, with snoring history, nocturnal apnea and chronic mouth breathing. All the children had OSAS confirmed by the sympton\'s presence and by the polysomnography and were divided into two groups: preoperative and postoperative (pacients that had OSAS diagnosed before the adenotonsillectomy,and were revaluated 12 months after. Both groups were submitted to maximum isometric tongue force, applied in the tip and in the back of the tongue, through the dynamometer and through the lateral radiography was performed a craniofacial evaluation and hyoid positioning. Results: In preoperative patients on linear regression the cephalometric measure D. vert. H presented strong and significant (p= 0,0083) negative relation with the tip of the tongue force. Whereas the back of the tongue before the surgery was not significant, for none of the variables. In postoperative patients the maximum isometric tongue force from the back and from the tip were significantly (p<0,0330 e p<0,0098 respectively) related to the cephalometric measure C3-H. The comparison between the cephalometric measures between the preoperative and postoperative groups and between the residual sub group and the healed ones, did not have difference in the hyoid\'s height (HYS, HYMP, D Vert.H) and on the hyoid\'s anteroposterior relation (D Horiz.H, C3-H). In regards to the maximum isometric tongue force from the extrinsic tongue musculature when compared to the average and standard deviation in patients pre and post surgery, it was noticed that there was difference for the tongue force measures (p= 0,0016 for the back and p=0,0041 for the tip) between them. There was no difference between the sub groups residual and healed. Conclusion: In the present study we can conclude that there is relation between the force of the lingual muscle and hyoid bone\'s position in children with OSAS. In other words, an increase on the pharynx dilator muscles\' strength can influence the hyoid\'s height in children with OSAS.
9

Neural drive to human respiratory muscles

Saboisky, Julian Peter, Clinical School - Prince of Wales Hospital, Faculty of Medicine, UNSW January 2008 (has links)
This thesis addresses the organisation of drive to human upper airway and inspiratory pump muscles. The characterisation of single motor unit activity is important as the discharge frequency or timing of discharge of each motor unit directly reflects the output of single motoneurones. Thus, the firing properties of a population of motor units is indicative of the neural drive to the motoneurone pool. The experiments presented in Chapter 2 measured the recruitment time of five inspiratory pump muscles (diaphragm, scalene, second parasternal intercostal, and third and fifth dorsal external intercostal muscles) during normal quiet breathing and quantified the timing and magnitude of drive reaching each muscle. Chapter 3 examined the EMG activity of a major upper airway muscle (the genioglossus). The single motor units of the genioglossus display activity that can be grouped into six types based on its association or lack of association with respiration. The types of activity are termed: Inspiratory Phasic, Inspiratory Tonic, Expiratory Phasic, Expiratory Tonic, Tonic, and Tonic Other. A new method is presented in Chapter 4 to illustrate large amounts of data from single motor units recorded from respiratory muscles in a concise manner. This single figure displays for each motor unit, the recruitment time and firing frequency, the peak discharge frequency and its time, and the derecruitment time and its frequency. This method, termed the time-and-frequency plot, is used to demonstrate differences in behaviour between populations of diaphragm (Chapter 2) and genioglossus (Chapter 3) motoneurones. In Chapter 5, genioglossus activity during quiet breathing is compared between a group of patients with severe OSA and healthy control subjects. The distribution of central drive is identical between the OSA and control subjects with the same proportion of the six types of motor unit activity in both groups. However, there are alterations in the onset time of Inspiratory Phasic and Inspiratory Tonic motor units in OSA subjects and their peak discharge rates are also altered. Single motor unit action potentials in OSA subjects showed an increased area. This suggests the presence of neurogenic changes and may provide a pathophysiological explanation for the increased multiunit electromyographic activity reported in OSA subjects during wakefulness.
10

Neural drive to human respiratory muscles

Saboisky, Julian Peter, Clinical School - Prince of Wales Hospital, Faculty of Medicine, UNSW January 2008 (has links)
This thesis addresses the organisation of drive to human upper airway and inspiratory pump muscles. The characterisation of single motor unit activity is important as the discharge frequency or timing of discharge of each motor unit directly reflects the output of single motoneurones. Thus, the firing properties of a population of motor units is indicative of the neural drive to the motoneurone pool. The experiments presented in Chapter 2 measured the recruitment time of five inspiratory pump muscles (diaphragm, scalene, second parasternal intercostal, and third and fifth dorsal external intercostal muscles) during normal quiet breathing and quantified the timing and magnitude of drive reaching each muscle. Chapter 3 examined the EMG activity of a major upper airway muscle (the genioglossus). The single motor units of the genioglossus display activity that can be grouped into six types based on its association or lack of association with respiration. The types of activity are termed: Inspiratory Phasic, Inspiratory Tonic, Expiratory Phasic, Expiratory Tonic, Tonic, and Tonic Other. A new method is presented in Chapter 4 to illustrate large amounts of data from single motor units recorded from respiratory muscles in a concise manner. This single figure displays for each motor unit, the recruitment time and firing frequency, the peak discharge frequency and its time, and the derecruitment time and its frequency. This method, termed the time-and-frequency plot, is used to demonstrate differences in behaviour between populations of diaphragm (Chapter 2) and genioglossus (Chapter 3) motoneurones. In Chapter 5, genioglossus activity during quiet breathing is compared between a group of patients with severe OSA and healthy control subjects. The distribution of central drive is identical between the OSA and control subjects with the same proportion of the six types of motor unit activity in both groups. However, there are alterations in the onset time of Inspiratory Phasic and Inspiratory Tonic motor units in OSA subjects and their peak discharge rates are also altered. Single motor unit action potentials in OSA subjects showed an increased area. This suggests the presence of neurogenic changes and may provide a pathophysiological explanation for the increased multiunit electromyographic activity reported in OSA subjects during wakefulness.

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