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Rössert, Christian Andreas. "Reverse engineering the vestibular system." Diss., lmu, 2010. http://nbn-resolving.de/urn:nbn:de:bvb:19-131165.
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Law, Tammy Che-Yan. "Recalibration of the vestibular system." Thesis, University of British Columbia, 2011. http://hdl.handle.net/2429/36344.
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The vestibular system conveys information regarding head motion to the central nervous system (CNS). Independently, this vestibular signal of head motion does not provide an absolute reference of head motion as the frequency coding of the afferent nerves is influenced by adaptation properties and nonlinearities. The optic flow signal of head rotation from the visual system however, is spatially encoded and can function as an absolute reference. The aim of this study was to determine if a visual signal of head rotation can recalibrate an altered vestibular signal of head motion during standing balance and to investigate the underlying mechanisms of this recalibration at the muscular level.
Eight healthy subjects were exposed to an electrical vestibular stimulus correlated to head movement (±0.125 mA/°/s) while standing on foam with eyes closed. This velocity-coupled vestibular stimulation (VcVS) was applied in a bipolar, bilateral orientation and depending on its polarity, resulted in the vestibular nerves coding for slower or faster head movements. Initially, this alteration of natural vestibular information destabilized subjects. During the conditioning phase, subjects opened their eyes and used visual information in combination with the new vestibular information to update their representation of self-orientation. Following this, subjects showed a significant decrease (~35%) in body sway while still receiving VcVS.
The mechanisms underlying vestibular recalibration were examined by observing how visuo-vestibular recalibration affected the vestibular-evoked muscular responses. Muscle activity was recorded in five subjects using surface electromyography (EMG) bilaterally on the medial gastrocnemius and tensor fascia latae muscles. Stochastic vestibular stimulation (SVS) in combination with VcVS was delivered to evoke biphasic muscular responses. Prior to the conditioning period, the peak amplitude of the response was significantly attenuated and then returned to control levels following conditioning.
Overall, these observations indicate that the vestibular system can be recalibrated by a visual signal of head rotation. This process is associated with an initial decrease in vestibular-evoked muscular responses which return to control levels once recalibration occurs. These results suggest that the CNS can modulate vestibular processes by down regulation or selective gating of vestibular signals in order to achieve vestibular recalibration.
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Huang, Chuen-Chane. "Biped robot with a vestibular system." Diss., Virginia Tech, 1991. http://hdl.handle.net/10919/39834.
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The kinematics and dynamics of two legged or biped walking is considered. The resulting governing equations include actuator torques for a robot and muscle generated torques for a human. These torques are those necessary at each joint of a leg, including the foot, for a successful stride. The equations are developed from a consistent set variables with respect to a single inertial reference frame. This single reference frame approach has not been used by previous investigators. Control of the joint torques makes biped walking an extraordinary complex problem from a dynamics and control viewpoint. The control scheme that is developed incorporates the use of the direction of gravity as an important element in the overall control. The inclusion of gravity in biped robot walking has not previously been properly considered in other works.
A way is described to separate gravity and acceleration which are measured by an accelerometer which is on the robot. This system incorporates the use of angular motion sensing of the robot segment that contains the linear accelerometers. This system was formulated based on human motion sensing and what probably is present in the human central nervous system for processing these signals.Ph. D.
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Tangorra, James Louis 1967. "System identification of the vestibular ocular reflex via visual and vestibular co-stimulation." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/29623.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2003.Includes bibliographical references (p. 317-321).
The study of eye motions involved in the vestibular ocular reflex (VOR) is a key tool for understanding the performance of the vestibular system and for the diagnosis of dysfunction. Limitations in experimental equipment and in the analytic methods applied have resulted in VOR testing being conducted under artificial laboratory conditions that do not resemble the conditions under which the VOR naturally functions. The results from these tests are often unreliable, and may, in fact, misrepresent the function and performance of the VOR and the vestibular system. The purpose of this thesis was to develop the experimental equipment, protocol, and analysis algorithms required to conduct a stochastic system identification of the horizontal, rotational VOR, while it was being used to stabilize gaze during natural, head-free tracking. By providing statistically uncorrelated stimuli to the visual and vestibular systems, estimates of the VOR's impulse response function could be made as subjects tracked a visual target that moved with an unpredictable trajectory. A novel stochastic technique was developed to generate the visual and vestibular input sequences such that they had appropriate amplitude distributions, and auto- and cross-correlation functions. The results showed that the technique was able to identify the dynamics of the VOR over the frequency range that it naturally functions to stabilize gaze, that is from below 0.5 Hz through 4.0 Hz. Nonlinearities in the head-neck control system limited the analysis at low frequencies, and difficulties in calculating high frequency eye velocities limited the accuracy of the analysis at high frequencies.
(cont.) Unlike the rotational VOR tests that are commonly used today, this technique was able to distinguish between the visually and vestibularly driven eye responses, and was able to show that during head-free gaze tracking, the vestibular system is able to compensate for head disturbances with a near unity gain.
by James Louis Tangorra.
Ph.D.
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Guilding, Clare. "Mechanisms of plasticity in the vestibular system." Thesis, University of Edinburgh, 2004. http://hdl.handle.net/1842/24655.
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This thesis describes a series of experiments in rat, designed to investigate the underlying molecular causes of VC. The role of the stress systems in the adaptive down-regulation of GABA receptors during compensation is investigated using biochemical and in vitro electrophysiological techniques. The results demonstrate that the down-regulation of GABA receptor efficacy in ipsilesional MVN neurones observed after 4h of compensation following a unilateral labyrinthecytomy (UL) is dependent on activation of glucocorticoid receptors. The enzyme, 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) regenerates active glucocorticoids from inert forms, and is found to be present in the central vestibulo-oculomotor centres of the brainstem and cerebellum. This suggests that this modulatory enzyme is likely to be involved in regulating the exposure of these centres to circulating glucocorticoids. The results show that the levels of 11β-HSD1 activity in the vestibulo-cerebellum and MVN are stable over the 4h period after UL, disapproving the hypothesis that changes in enzyme modulatory activity may occur in parallel with the deafferentation induced changes in the properties of the ipsilesional MVN over this time. The relative importance of intrinsic membrane properties versus synaptic inputs, to the spontaneous firing rate of ipsilateral MVN neurones is investigated at varying times following UL. The endogenous activity of MVN neurones is assessed by their spontaneous activity recorded in brainstem slices perfused with a cocktail of neurotransmitter antagonists to block synaptic transmission. The results demonstrate a significant increase in excitability of lesioned rostral MVN neurones at 4h post-UL, which is maintained primarily by changes in the intrinsic pacemaker properties of these neurones. At 48h and 1wk post-UL the significant increase in excitability of lesioned rostral MVN neurones is sustained, however by this time it is maintained by an increased excitatory synaptic input onto the neurones. Thus different mechanisms are utilised in the initiation and maintenance of processes involved in VC.
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Stanley, N. J. "Integrin expression in the mouse vestibular system." Thesis, University College London (University of London), 2013. http://discovery.ucl.ac.uk/1393280/.
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The mammalian utricle has shown limited capacity for spontaneous regeneration of hair cells within a damaged sensory epithelium. In vivo and in vitro exposure of the tissue to ototoxic aminoglycosides has been utilised to induce hair cell loss, in order to study these regenerative events. The mammalian utricle is believed to regenerate hair cells by the direct transdifferentiation of supporting cells without a mitotic event. The cellular and molecular mechanisms behind this regenerative capability continue to be the subject of inner ear research. The integrin family of cell surface receptors are known for their key role in cellular adhesion, both to the extracellular matrix and to neighbouring cells. Studies of integrins have shown that they are also involved in numerous cellular processes including proliferation, differentiation and migration. They are therefore a likely candidate for involvement in the cellular events which underlie the regenerative ability demonstrated by the mammalian utricle. This study has identified a subset of the mammalian integrin subunits as being present in the normal adult mouse utricle. The identification of these integrins was achieved by both degenerate PCR and qPCR screening of utricular cDNA. Through immunohistochemistry, β1 and α6 have been shown to localise at the basement membrane of normal utricular tissue. Integrins β3 and β5 appear to be expressed within vestibular hair cells. Integrins β1, αV, β5, β3 and α6 are also present within the mesenchyme. The utricular macula of adult mice was utilised as an in vitro model in order to induce hair cell loss by gentamicin treatment and investigate integrin expression in the utricle during this process and subsequent regeneration. Relative quantification of qPCR data has indicated that a number of integrins including β1, αV and β3 show an increase in expression level at 4 days post treatment. Immunohistochemistry shows some changes in integrin localisation between 4 and 21 days post-gentamicin.
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Hall, Courtney D., Dara Meldrum, Gary P. Jacobson, and Neil T. T. Shephard. "The Aging Vestibular System: Implications for Rehabilitation." Digital Commons @ East Tennessee State University, 2015. https://dc.etsu.edu/etsu-works/476.
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Book Summary: Balance Function Assessment and Management, now in its second edition, continues to comprehensively address the assessment and treatment of balance system impairments through contributions from top experts in the areas of dizziness and vertigo. Designed for use in graduate audiology programs and by practicing audiologists, this is also a valuable text for those in the fields of physical therapy, otolaryngology, and neurology. Assessment chapters focus on ocular motility testing, positional/positioning testing, caloric testing, rotational testing, computerized dynamic posturography, and vestibular evoked potentials. Treatment chapters examine nonmedical, medical, and surgical treatments of dizziness and vertigo, vestibular rehabilitation, and assessment of and intervention for risk of falls. Additionally, this text provides background information on the vestibular and ocular motor systems with corresponding sample cases. New topics addressed in this edition include: Development of the vestibular system Central compensation following peripheral vestibular system impairment Video head impulse test (vHIT) Biomechanics and physiology of balance Electrocochleography (ECochG) Pediatric vestibular system and balance assessment Effects of age on the vestibular and balance systems
An added bonus to the second edition is the companion website that offers additional reference materials, such as video clips, associated with the text.
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Akin, Faith W. "Effects of Aging on the Vestibular System." Digital Commons @ East Tennessee State University, 2010. https://dc.etsu.edu/etsu-works/2443.
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Cirmirakis, D. "Novel telemetry system for closed loop vestibular prosthesis." Thesis, University College London (University of London), 2013. http://discovery.ucl.ac.uk/1389947/.
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Disorders of the vestibular system result in loss of body balance and a steady vision in humans and animals. The most common consequences include vertigo, oscillopsia, postural instability and blurred vision. Currently, conventional medicine cannot cure the damage or restore the function of the vestibular system. Vestibular prosthesis may assist in restoring its function using electrical stimulation, which involves delivering current pulses into the nerves innervating the semi-circular canals in the inner ear. A vestibular prosthesis contains external electronics and an implantable medical device . The system delivers modulated electrical pulses and stimulates vestibular nerves with these pulses to inform the brain about the motion. Power transfer to, and communication with the implanted device, is provided by telemetry. In biomedical implanted devices the telemetry is usually implemented by radio-frequency induction using weakly coupled coils. Using a single set of coils for simultaneous power transfer and communication creates the challenge of contradicting requirements. For high data rates the inductive link must have a wide bandwidth but power transfer requires a low bandwidth. Moreover by modulating a carrier the power transfer is degraded. This thesis describes the design, implementation and experimental evaluation of a novel telemetry system for a three-dimensional vestibular prosthesis with neural recording. The developed telemetry system uses a single pair of inductively-coupled coils to power-up the implant and maintain bi-directional communication to control its operation. It also relays raw electroneurogram (ENG) data out of the body at high speed. For inductive power control two methods are combined: a geometrical approach and a feedback loop to maintain a constant level of delivered power. The communication to the implant (downlink) is obtained by amplitude modulation while the communication from the implant to the external transmitter (uplink) uses passive phase shift modulation. On-chip humidity sensing capabilities are facilitated in the implant microelectronics to monitor hermeticity of the package. The uplink achieves the highest data speed demonstrated in the literature of available methods using a single set of coils with combined power and communication links. The developed technique can be applied to other applications including RFID.
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Hall, Courtney D., and Susan J. Herdman. "Balance Function and Dysfunction and the Vestibular System." Digital Commons @ East Tennessee State University, 2014. https://dc.etsu.edu/etsu-works/443.
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Book Summary: In two freestanding but linked volumes, Textbook of Neural Repair and Rehabilitation provides comprehensive coverage of the science and practice of neurological rehabilitation. This volume, Medical Neurorehabilitation, can stand alone as a clinical handbook for neurorehabilitation. It covers the practical applications of the basic science principles presented in volume 1, provides authoritative guidelines on the management of disabling symptoms, and describes comprehensive rehabilitation approaches for the major categories of disabling neurological disorders. Emphasizing the integration of basic and clinical knowledge, this book and its companion are edited and written by leading international authorities. Together they are an essential resource for neuroscientists and provide a foundation for the work of clinical neurorehabilitation professionals.
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Ferreira, Ricardo Filipe da Silva. "Síndrome vestibular em canídeos." Bachelor's thesis, Universidade Técnica de Lisboa. Faculdade de Medicina Veterinária, 2009. http://hdl.handle.net/10400.5/1623.
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Dissertação de Mestrado Integrado em Medicina VeterináriaA síndrome vestibular é uma apresentação neurológica relativamente comum em Medicina Veterinária. É definida como o conjunto de sinais clínicos associados a uma doença do sistema vestibular. A função do sistema vestibular é traduzir as forças de gravidade e movimento em sinais neurológicos utilizados pelo encéfalo para a determinação da posição da cabeça no espaço, e para a coordenação dos movimentos da cabeça com os reflexos motores responsáveis pela estabilidade postural e ocular. Desta forma, afecções do sistema vestibular resultam, frequentemente, em alterações posturais da cabeça e corpo, descoordenação motora e ataxia, e alterações nos movimentos oculares. O sistema vestibular é constituído por dois componentes funcionais: o componente periférico, localizado no ouvido interno e no qual se incluem os receptores sensoriais localizados no labirinto membranáceo e a porção vestibular do nervo craniano VIII; e o componente central, localizado no tronco cerebral e cerebelo, e no qual se incluem os núcleos e feixes vestibulares. Os cães com doença vestibular central apresentam, tipicamente, sinais clínicos adicionais que reflectem envolvimento do tronco cerebral. Estes podem incluir défices dos nervos cranianos, parésia, défices nas reacções posturais e estado mental alterado. É assim possível a diferenciação clínica entre a síndrome vestibular periférica e a síndrome vestibular central. Este é, aliás, o passo fundamental para a realização de um diagnóstico diferencial adequado, um plano diagnóstico e terapêutico correcto, assim como para elaborar considerações sobre o prognóstico. O protocolo terapêutico e o prognóstico são directamente dependentes da etiologia da disfunção vestibular, apresentando, por isso, grande variabilidade. As duas afecções mais comuns, que causam disfunção vestibular central, são neoplasias e infecção / inflamação; enquanto que em pacientes com sinais vestibulares periféricos, a otite média / interna e a doença vestibular idiopática são os diagnósticos mais frequentes. A componente prática da presente dissertação incide na descrição e análise de 8 canídeos apresentados à consulta no Hospital Escolar da Faculdade de Medicina Veterinária da Universidade Técnica de Lisboa, com síndrome vestibular. Foram observados 5 canídeos com síndrome vestibular periférica, um deles com afecção bilateral do sistema vestibular, e 3 canídeos com síndrome vestibular central. Apesar de algumas dificuldades terem limitado, nalguns casos, a obtenção de um diagnóstico etiológico definitivo, a realização de um diagnóstico anatómico correcto foi possível na maioria dos casos.
ABSTRACT - CANINE VESTIBULAR SYNDROME - Vestibular syndrome is a relatively common neurologic presentation in Veterinary Medicine. It is defined as a combination of clinical signs associated with disease of the vestibular system. The function of the vestibular system is to transduce the forces of gravity and movement into neurologic signals that the brain can use to determine the position of the head in space, and to coordinate head movements with the motor reflexes responsible for postural and ocular stability. Thus, lesions of the vestibular system commonly result in abnormal posture of the head and body, motor incoordination and ataxia, and abnormal eye movements. The vestibular system is composed of two functional components: the peripheral component, located in the inner ear, include the sensory receptors located in the membranous labyrinth and the vestibular portion of cranial nerve VIII; and the central component, located in the brainstem and cerebellum, include vestibular nuclei and pathways. Dogs with central vestibular disease typically have additional clinical signs reflective of brainstem involvement. These can include deficits of cranial nerves, paresis, postural reaction deficits and altered mental status. It is then possible to clinically differentiate peripheral vestibular syndrome from central vestibular syndrome. In fact, this is the fundamental step in the elaboration of a proper differential diagnosis, an accurate diagnostic and therapeutical plan, and in the elaboration of prognostic considerations. The treatment and prognosis are directly dependent of the vestibular dysfunction aetiology, thus presenting great variability. The two most common disease processes that cause central vestibular dysfunction are neoplasia and infection / inflammation; whilst the two most common diagnoses in patients with peripheral vestibular signs are otitis media / interna and idiopathic vestibular disease. The practical component of this thesis concerns the study of 8 dogs presented with vestibular syndrome, at the Faculty of Veterinary Medicine Teaching Hospital. Five dogs with peripheral vestibular syndrome, one of which with bilateral disease of the vestibular system, and 3 dogs with central vestibular syndrome were observed. Despite some limitations in the attainment of a definitive etiologic diagnosis in some cases, an accurate anatomic diagnosis was possible in most cases.
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Peixoto, Ana Filipa de Sousa Maia Sequeira. "Síndrome vestibular periférica em cães." Master's thesis, Universidade de Évora, 2022. http://hdl.handle.net/10174/31205.
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O presente relatório de estágio foi redigido no âmbito do estágio curricular do Mestrado Integrado em Medicina Veterinária e está dividido em quatro secções. O relatório de casuística aborda as atividades desenvolvidas na área de clínica e cirurgia de animais de companhia durante cinco meses, no Hospital Veterinário da Trofa. A monografia consiste numa revisão bibliográfica sobre a síndrome vestibular periférica em cães, e é seguida pela exposição e discussão de um caso clínico do mesmo tema.
Nos cães, a síndrome vestibular periférica deve-se principalmente a otite média-interna, síndrome vestibular periférica idiopática, neoplasia aural, hipotiroidismo, exposição a tóxicos ou doença vestibular congénita. Os animais podem surgir com inclinação cefálica, nistagmo patológico, estrabismo vestibular, ataxia vestibular e paralisia do nervo facial. Os exames complementares de diagnóstico incluem o exame otoscópico, miringotomia, radiografia e tomografia computorizada. O tratamento deve dirigir-se à etiologia identificada; Abstract: Peripheral Vestibular Syndrome in Dogs
The current report was carried out within the scope of the Master’s Degree in Veterinary Medicine’s curricular internship and is divided in four sections. The casuistic report goes over the activities followed in small animal practice and surgery throughout five months in the Trofa Veterinary Hospital. The monograph consists of a bibliographic review about peripheral vestibular syndrome in dogs, and is followed by a case report concerning the same subject and its discussion.
In dogs, peripheral vestibular syndrome is caused mainly by otitis media-interna, idiopathic peripheral vestibular syndrome, aural neoplasia, hypothyroidism, toxic exposure or congenital vestibular disease. Animals may present with head tilt, pathological nystagmus, vestibular strabismus, vestibular ataxia and facial nerve paralysis. Complementary diagnostic exams include otoscopic examination, myringotomy, radiography and computerized tomography. Treatment must focus on the identified etiology.
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Hussain, Kiran. "The expression of integrins in the human vestibular system." Thesis, University College London (University of London), 2018. http://discovery.ucl.ac.uk/10057468/.
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The inner ear is responsible for the detection of sound and movement and therefore subserves hearing and balance. The vestibular system is an integral part of the labyrinth that is housed in the otic capsule of the petrous temporal bone. It is made up of five end organs; the three semiHcircular canals, the utricle and saccule. Mechanoreceptive hair cells, supporting cells and nerve endings make up the sensory neuroepithelia of these organs. Loss of the hair cells in the cochlea leads to deafness and loss in the vestibular system causes balance dysfunction, dizziness and vertigo. Unlike in the cochlea, when this loss occurs in the vestibular system there is in fact a limited capacity for regeneration in mammals. Following hair cell loss induced by ototoxic insult, both in vivo and in vitro, some new hair cells can arise spontaneously. In vivo approximately one third of the hair cells might be replaced with spontaneous reHinnervation. The regenerated new hair cells may be due to the direct phenotypic conversion of supporting cell into hair cells without an intervening mitotic event. Integrins are cell adhesion receptors that play important roles in physiological and pathological processes throughout the body including the vestibular system. The 24 αβ heterodimeric members mediate the interaction of cell - cell transmissions as well as cell H extracellular matrix communication. With specific reference to the vestibular system the role of integrins is potentially integral to the repair and recovery process. The lesion created by the death of a hair cell is closed by supporting cells in a manner that maintains the permeability barrier at the luminal surface of the epithelium. This controlled process relies on cell shape changes and spreading that likely involves integrins. Furthermore, the supporting cells remove these dead hair cells by a phagocytic process. Certain integrins are expressed at the surface of cells that recognise apoptotic cells. Their role in the vestibular system in particular has the potential to provide insight into how disorders of this complex system can be better understood and managed. To date this has not been studied in humans. Explant cultures of vestibular tissue is the only means to perform experimental studies upon the viable human ear. The sensory tissues from the human vestibular system can be obtained from patients undergoing trans labyrinthine procedures for acoustic neuromas. Previous work has shown that they can be maintained ex corporeally in explant culture for periods of up to four weeks. This provides a unique opportunity to study this complex system in humans. This study has identified which integrin subunits are present in the human utricle and localised them. The change in their expression and location following ototoxic injury has also been demonstrated. Crucially, α2, α6, α8, αV, β1 and β5 were located to the basement membrane. α6, αV, β1, β3 β5 and β6 all individually demonstrate interesting patterns and have been implicated in previous work, not just limited to within the inner ear, as playing a potential role in the regenerative processes that occur.
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Navarro, Morales Deborah. "Τhe influence οf the vestibular system οn time perceptiοn." Electronic Thesis or Diss., Normandie, 2025. https://theses.hal.science/tel-05000089.
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Au niveau perceptif, le temps n’est pas une métrique constante régie par le tic-tac d’une horloge. Les distorsions temporelles surviennent en raison de divers facteurs comme le manque d’attention, les émotions, le manque de sommeil, l’excitation, le mouvement, entre autres. Cette thèse vise à explorer comment le système vestibulaire influence la perception du temps. Dans le premier axe de cette thèse deux études ont été réalisées lors des missions spatiales de longue durée. Nous avons trouvé que les astronautes à bord de la Station Spatiale Internationale estiment correctement les intervalles de temps dans l’échelle de jours, ils surestiment le temps dans les durées de secondes à minutes et sous-estiment le temps dans l’échelle des heures. Etant donné que les distorsions temporelles dans l’espace peuvent provenir de plusieurs sources, nous avons décidé de mener une tâche spécifique du système vestibulaire. Le deuxième axe comprend deux études sur la perception du temps lors de stimulations vestibulaires, en se concentrant sur les rotations corporelles. Dans la première étude, nous avons constaté que le temps perçu durant les rotations est sous-estimé par rapport aux conditions statiques chez les sujets en bonne santé. Dans la deuxième étude, nous avons confirmé que cet effet est vestibulaire, car il est absent chez les patients atteints de vestibulopathie bilatérale. Nos résultats suggèrent que la perception du temps dépend des entrées vestibulaires : lorsque ces entrées diminuent, le temps perçu est surestimé ; lorsque ces entrées augmentent (stimulées), le temps perçu est sous-estiméAt the perceptual level, time is not a constant metric defined by the ticks of a clock. Distortions in time perception occur due to various factors, including attention deficits, emotions, sleep deprivation, arousal, motion, and others. This thesis explores how the vestibular system influences time perception. In the first part of the thesis, two studies were conducted during long-term space missions. We found that astronauts aboard the International Space Station accurately estimate short time delays over days. However, they tend to overestimate durations ranging from seconds to minutes and underestimate durations on the scale of hours. Given that time distortions in space can arise from multiple sources, we conducted a specific vestibular task to isolate the vestibular contribution. The second part of the thesis includes two studies on time perception during vestibular stimulation, focusing on whole-body rotations. In the first study, we found that time during rotations is underestimated compared to static conditions in healthy subjects. In the second study, we confirmed that this time underestimation was vestibular, as it was absent in Bilateral Vestibulopathy patients. Our findings suggest that time perception depends on vestibular inputs: when vestibular inputs are decreased, perceived time is overestimated; when vestibular inputs are increased (stimulated), perceived time is underestimated
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Sales, Renata. "Achados da acuidade visual estática e dinâmica em pacientes com disfunção vestibular." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/17/17150/tde-22102013-144514/.
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SALES, R. Achados da acuidade visual estática e dinâmica em pacientes com disfunção vestibular. 106f. Tese (Doutorado) da Faculdade de Medicina de Ribeirão Preto-USP. Ribeirão Preto-SP, 2013. Para a obtenção da visão nítida é necessário que a imagem permaneça estável na retina, mesmo com a movimentação cefálica. As pessoas que sofrem de labirintopatias são mais sensíveis a efeitos visuais, podendo apresentar os sintomas de tontura, enjoo e oscilopsia durante a movimentação cefálica. Esse fato ocorre devido ao conflito sensorial entre o sistema vestibular e visual. O presente estudo objetivou verificar a variação da acuidade visual estática e dinâmica em pacientes com disfunção vestibular. Foram selecionados pacientes de ambos os sexos, com idade entre 14 e 88 anos de idade submetidos ao exame de vetoeletronistagmografia entre os anos de 2009 e 2011. Esses pacientes também foram submetidos ao exame de acuidade visual estática e dinâmica. Na acuidade visual dinâmica, foram pré-determinadas frequências de 0.5, 1.0, 1.5 e 2.0 Hertz para a movimentação cefálica. Os resultados mostraram maior decréscimo da acuidade visual estática e dinâmica entre os pacientes com labirintopatias bilaterais se comparadas com as unilaterais e o grupo controle. Além disso, o aumento da frequência produziu decréscimo da acuidade visual em todos os grupos e a posição da movimentação cefálica na vertical mostrou maior sensibilidade se comparada à horizontal. Pôde-se concluir que os pacientes com labirintopatias apresentaram decréscimo da acuidade visual estática e dinâmica, principalmente nas frequências mais altas e com a movimentação cefálica na posição vertical, sendo esses exames importantes para auxiliar no diagnóstico e monitoramento das labirintopatias. Palavras-chave: Acuidade visual; Sistema vestibularFor obtaining an accurate image is necessary that remains stable on the retina, even with head movement. People suffering from labyrinthopathy are more sensitive to visual effects, and may have symptoms of dizziness, nausea and oscillopsia during head movement. This fact occurs because the sensory conflict between visual and vestibular system. The present study aimed to determine the variation of static and dynamic visual acuity in patients with vestibular dysfunction. Selected patients were of both gender, aged between 14 and 88 years old who underwent examination vetoeletronistagmografia between the years 2009 and 2011 at the home Institution. The patients were subjected to tests of visual acuity static and dynamic. In dynamic visual acuity, were predetermined frequencies of 0.5, 1.0, 1.5 and 2.0 Hz for the patient\'s head movement. The results showed a greater decrease in static and dynamic visual acuity among patients with bilateral labyrinthopathy compared with the unilateral and control groups. In addition, the frequency increase produced decreased visual acuity in all groups and the position of head movement in the vertical showed a higher sensitivity compared to the horizontal. It was concluded that patients with labyrinthopathy showed a decrease of static and dynamic visual acuity, especially at higher frequencies and with head movement in a vertical position, and these important tests to assist in diagnosis and monitoring of the labyrinthopathy. Keywords: Visual acuity; Vestibular system
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Brooks, Jessica. "How actions alter sensory processing: reafference cancellation in the vestibular system." Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=106238.
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Our sensory systems are continually confronted with the task of differentiating sensory inputs due to external events (exafference) from sensory information due to our own actions (reafference). Discriminating between these two types of stimuli is critical in order to achieve accurate perception and motor control. The current mechanism that explains how the vestibular system deals with this issue states that during an active movement, a prediction of the sensory consequences of motor commands computed by an internal model is compared to the actual sensory feedback; if the internal model's prediction and sensory feedback match, the vestibular signal is cancelled, if they do not, the vestibular signal is left unaltered. The studies presented in this thesis were aimed at understanding this fundamental mechanism. In particular, I investigate 1- the rules that govern the cancellation of vestibular reafference, 2- the adaptability of the internal model that underlies vestibular reafference cancellation and 3-the role of the vestibular cerebellum in the processing of passive and active motion. First, I establish that disrupting sensory feedback during an active movement affects the ability of central vestibular neurons to suppress vestibular reafference. Specifically, when proprioceptive feedback is disrupted during an active movement, vestibular reafference is no longer suppressed. In addition, I demonstrate that vestibular reafference due to active body movements are suppressed at the first central stage of vestibular processing. Second, I demonstrate that the internal model underlying the suppression of vestibular reafference adapts such that vestibular neurons regain the ability to suppress vestibular reafference in conditions when the relationship between motor commands and the actual head movements are altered. My findings strongly suggest that indeed the internal model used to predict the sensory consequences of motor commands is quickly updated when faced with new relationships between expected and actual sensory feedback.Finally, I examine the role that the cerebellum plays in the encoding of passive versus active motion. I found that in the passive condition, neurons in the rostral fastigial nucleus (FN) encode two separate representations of motion; half the neurons encode head motion and the other half encodes body motion. The neurons in the rostral FN that encode body movements provide the first neuronal correlate for the perception of body motion. Then I address how vestibular information is processed by the rostral FN during active movements. We found that neurons in the vestibular cerebellum were attenuated during active head and body motion and demonstrate for the first time that the primate cerebellum explicitly encodes the detailed time course of exafference. Taken together the results in this thesis provide firm evidence that vestibular reafference is suppressed during active head and body motion by a mechanism that compares the brain's internally generated expectation of the consequences of voluntary movements with the actual incoming sensory information.Nos systèmes sensoriels doivent continuellement faire la différence entre des sensations dues aux événements extérieurs (exaférence) et des sensations provoquées par nos propres actions (réafférence). Faire la différence entre ces deux types de stimuli est essential pour permettre une perception et un control moteur précis. Cette distinction est possible, au niveau du système vestibulaire, grâce au fait qu'une prédiction des conséquences sensorielles de la commande motrice évaluée par un modèle interne est comparée avec le retour sensorielle réel; si la prédiction du model interne est similaire au retour sensoriel, le signale vestibulaire est supprimé; si ils sont différent, le signal vestibulaire n'est pas altéré. Les études présentées dans cette thèse ont pour but de comprendre ce mécanisme fondamental. Plus particulièrement, je cherche a établir 1- les règles qui gouvernent la suppression des réafférences vestibulaire, 2- l'adaptabilité du modèle interne qui sous-tend la suppression des réafférences vestibulaire et 3- le rôle du cervelet vestibulaire dans le processus de différentiation des mouvements actif et passif.Premièrement, j'ai montré que déranger le retour sensoriel pendant un mouvement actif perturbe la capacité des neurones vestibulaire centraux à supprimer les réafférences vestibulaire. Plus précisément, quand le retour proprioceptif est perturbé pendant un mouvement actif, le retour vestibulaire n'est plus supprimé. De plus, j'ai démontré que le retour vestibulaire due à des mouvements du corps est aussi supprimé au premier niveau central du traitement vestibulaire.Deuxièmement, j'ai démontré que le model interne sous-tendant la suppression des réafférences vestibulaire s'adapte pour que les neurones vestibulaire retrouvent leur capacité à supprimer les réafférences vestibulaire dans des conditions ou la relation entre la commande motrice et le mouvement de la tète sont perturbé. Mes résultats suggèrent fortement que le model interne utilisé pour prédire les conséquences sensorielles de la commande motrice est rapidement mis a jour quand il est en présence de nouvelles relations entre retour sensoriel attendu et réel. Finalement, je me suis intéressé au rôle que joue le cervelet pour encoder les mouvements passif et actif. J'ai trouvé qu'en condition passive, les neurones du noyau rostral de fastigial (FN rostral) encodent deux représentations différentes du mouvement; la moitié des neurones encodent les mouvements de la tète et l'autre moitié encode les mouvements du corps. Les neurones du FN rostral qui encodent les mouvements du corps fournissent le premier corrélat neural de la perception des mouvements du corps. Puis j'aborde la question de comment l'information vestibulaire est traite par le FN rostral pendant les mouvements actifs? Nous avons trouvé que la réponse des neurones dans le cervelet vestibulaire est atténuée pendant les mouvements actifs de la tète et du corps. Cela démontre pour la première fois que le cervelet des primates encode les exafférences.Dans leur ensemble les résultats de cette thèse fournissent des évidences solides en faveur de la suppression des réafférences vestibulaire pendant les mouvements actifs de la tète et du corps. Cette suppression est possible grâce à un mécanisme qui compare les prévisions des conséquences d'un mouvement volontaire générées par le cerveau avec le retour sensoriel réel.
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Amenabar, Katharine. "Closed loop system identification of postural control with bilateral vestibular loss." College Park, Md.: University of Maryland, 2009. http://hdl.handle.net/1903/9686.
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Thesis (M.A.) -- University of Maryland, College Park, 2009.Thesis research directed by: Dept. of Kinesiology. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Silber, Joseph Allan. "Analysis of Vestibular Hair Cell Bundle Mechanics Using Finite Element Modeling." Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/9704.
Full textAbstract:
The vestibular system of vertebrates consists of the utricle, saccule, and the semicircular canals. Head movement causes deformation of hair cell bundles in these organs, which translate this mechanical stimulus into an electrical response sent to the nervous system.
This study consisted of two sections, both utilizing a Fortran-based finite element program to study hair cell bundle response. In the first part, the effects of variations in geometry and material properties on bundle mechanical response were studied. Six real cells from the red eared slider turtle utricle were modeled and their response to a gradually increased point load was analyzed. Bundle stiffness and tip link tension distributions were the primary data examined.
The cells fell into two groups based on stiffness. All cells exhibited an increase in stiffness as the applied load was increased, but cells in the stiffer group showed a greater increase. Tip link tensions in the compliant group were approximately 3 times as high as those in the stiffer group. Cells in the stiffer group were larger, with more cilia, and also had a higher stereocilia/kinocilium height ratio than the cells in the other group. The stereocilia/kinocilium height ratio was the most important geometric factor in influencing bundle stiffness. Modeling a bundle as just its middle row of stereocilia resulted in some decrease in stiffness, but more significantly, a stiffness that was virtually constant as applied load increased. Tip link tension distributions showed serial behavior in the core rows of stereocilia and parallel behavior in the outer rows; this trend intensified if the tip link elastic modulus was increased. It was demonstrated that full three-dimensional modeling of bundles is critical for obtaining complete and accurate results.
In the second part of the study, tip link ion gates were modeled. Sufficient tension in a tip link caused that link's ion gate to open, increasing the length of the link and causing its tension to decrease or the link to go slack. The two parameters that were varied were tip link elastic modulus and tip link gating distance d (change in length of the link). Bundle stiffness drops of up to 25% were obtained, but only when tip links went slack after gate opening; tip link slackening was dependent on tip link gating distance. Higher tip link modulus resulted in higher stiffness drops. Variable tip link modulus and tip link pre-tensioning were modeled. Variable tip link modulus resulted in increased bundle stiffness, especially under high applied loads, and in some cases, resulted in greater bundle stiffness drops when ion gates opened. Tip link pre-tensioning had no noticeable effect on bundle response. No evidence against inclusion of pre-tensioning or variable tip link elastic modulus was found.Master of Science
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Pasquier, Florane. "Etude de l'implication de la fonction vestibulaire dans la rythmicité biologique chez l'Homme." Thesis, Normandie, 2020. http://www.theses.fr/2020NORMC201.
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L’objectif de ce travail de thèse était de tester si la stimulation vestibulaire peut influencer les rythmes biologiques circadiens chez l’Homme. Pour répondre à cet objectif, nous avons évalué les effets de deux techniques de stimulation vestibulaire (fauteuil rotatoire et Stimulation Vestibulaire Galvanique/SVG) sur le rythme de l’activité motrice de sujets jeunes sains. Ce projet a également évalué la tolérabilité des protocoles appliqués. La proximité de la technique de SVG avec la stimulation transcrânienne à courant direct (tDCS) utilisée dans les troubles de l’humeur ainsi que les liens entre les troubles des rythmes biologiques et de l’humeur nous ont conduits à évaluer les effets de la stimulation vestibulaire sur le niveau d’anxiété.Une première étude a permis de démontrer que la stimulation induite par un fauteuil rotatoire en fin de journée provoque une diminution du niveau d’activité motrice, ainsi qu’une avance de phase du rythme de l’activité motrice deux jours après la stimulation. Une seconde étude a montré que la SVG appliquée en milieu de journée n’a pas d’effets significatifs sur le rythme de l’activité motrice et la transition entre les états de veille et de sommeil. Enfin, une troisième étude a permis de montrer que la SVG diminue le niveau d’anxiété et que cet effet dépend des paramètres de stimulation appliqués (durée). La technique de SVG est bien tolérée par les participants contrairement à la stimulation sur fauteuil rotatoire qui provoque une augmentation des symptômes de mal des transports.Ces résultats confirment que la stimulation vestibulaire peut être utilisée pour moduler les rythmes biologiques et l’humeur chez l’Homme. Cependant, les effets observés dépendent des paramètres de stimulation appliqués (technique de stimulation, moment de la journée). Ces résultats encouragent la poursuite des investigations concernant l’utilisation de la stimulation vestibulaire comme synchroniseur des rythmes biologiques et la SVG comme outil potentiel de réhabilitation des rythmes biologiques et de l’humeurThe main objective of this thesis was to test if the vestibular stimulation can impact the circadian biological rhythms in human. We have evaluated the effects of two vestibular stimulation methods (rotatory chair, Galvanic Vestibular Stimulation/GVS) on the motor activity rhythm of young healthy adults. This project also evaluated tolerability of the stimulation protocols. The similarities between GVS and transcranial Direct Current Stimulation (tDCS) used in the treatment of depression, and the links between biological rhythms disorders and mood disorders, have led us to assess the effects of vestibular stimulation on the anxiety level.Effects of vestibular stimulation induced by a rotatory chair at the end of the afternoon has been tested in the first study. We observed a decrease in motor activity level after the vestibular stimulation, and a phase advance effect two days after the stimulation. The second study demonstrated no significant effects of the GVS applied in the middle of the day on the motor activity rhythm, and the wake/sleep transition. Finally, the third study showed that GVS can decrease the anxiety level. This effect depends on the stimulation parameters (duration). GVS method was well tolerated by the participants. On the contrary, the rotatory chair induced motion sickness symptoms.These results confirm the influence of vestibular stimulation on biological rhythms and mood in human. However, the observed effects depend on the stimulation parameters (technique, time of the day). These results promote studies about the use of vestibular stimulation in the regulation of biological rhythms, and the GVS in the treatment of the biological rhythms and mood disorders
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Beuter, Cláudia Regina. "AVALIAÇÃO VESTIBULAR NO RECÉM-NASCIDO DE TERMO." Universidade Federal de Santa Maria, 2007. http://repositorio.ufsm.br/handle/1/6585.
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A transverse study in term newborns was made to determine the occurrence of motor responses and possible asymmetries during the stimulation of the vestibular system through the head turning after release from the midline and passive rotation. From October to December of 2005, 320 neonates were admitted to the Adjacent Lodgings of the University Hospital of Santa Maria. From those, 89 were selected for assessment of the vestibular function since they have previously had fetal static control through ultrasound. Our results show that right-sided head lateralization was significantly greater than left-sided. The predominancy of the lateralization towards the right side also occurred in the male gender, cephalic presentations and left-sided back, however,
not significant. On the passive rotation about the vertical axis, the great majority of the neonates presented eye deviation in the opposite direction of the body movement and
about the horizontal axis, the great majority of them either remained with their eyes closed or did not present any deviation at all. Results corroborate with the existing literature and suggest an association between fetal static and vestibular function. It was shown through vestibular stimulation trials that term newborns already possess a functional asymmetry as well as motor responses to this system stimulationCom o objetivo determinar a ocorrência de respostas motoras e possíveis assimetrias durante a estimulação do sistema vestibular pelas provas de queda da cabeça e rotação passiva, foi realizado um estudo transversal no recém-nascido de termo. No período de outubro a dezembro de 2005, 320 recém-nascidos foram admitidos no Alojamento Conjunto do Hospital Universitário de Santa Maria, e destes 89 foram selecionados para avaliação da função vestibular, por terem feito controle da estática fetal através do ultra-som. Nossos resultados mostram que a lateralização da cabeça para a direita foi significativamente maior do que para esquerda. Este predomínio da lateralização para a direita também ocorreu no gênero masculino, nas apresentações cefálicas e com o dorso para esquerda, no entanto estes não foram significativos. Nas provas de rotação passiva na vertical a grande maioria dos RN apresentou o desvio dos olhos sempre no sentido oposto ao movimento do corpo e no plano horizontal, a grande maioria dos RN permaneceu com os olhos fechados, ou não apresentou desvio algum. Nossos resultados corroboram com a literatura existente, e sugerem uma associação entre a estática fetal e a função vestibular. Através das provas de estimulação vestibular, ficou demonstrado que o RN de termo já possui respostas motoras a estimulação deste sistema, bem como uma assimetria funcional
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Toreyin, Hakan. "Design of a low-power interface circuitry for a vestibular prosthesis system." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/54018.
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The human vestibular system is responsible for maintaining balance and orientation, and stabilizing gaze during head motion. Head motion is sensed by vestibular sensors and encoded via the firing rate of vestibular neurons. Vestibular disorders can result in dizziness, imbalance, and disequilibrium. Currently there are no therapeutic options for individuals suffering from bilateral vestibular dysfunction. A potential solution is a vestibular prosthesis (VP). This device serves to replace peripheral vestibular organs by sensing angular motion, detected by semicircular canals (SCCs), and linear head motion, detected by the otolith organs, and selectively stimulating the corresponding vestibular afferents. An ideal VP will not only mimic the patient-dependent vestibular neural dynamics, but also consume low power. In this study, three energy-efficient ways to implement the motion encoding function required in a vestibular prosthesis are presented. Both analog and digital signal processing techniques to implement the vestibular signal processing functions are investigated.
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Bhatti, Pamela T., Susan J. Herdman, Siddarth Datta Roy, Courtney D. Hall, and Ronald J. Tusa. "A Prototype Head-Motion Monitoring System for In-Home Vestibular Rehabilitation Therapy." Digital Commons @ East Tennessee State University, 2012. https://dc.etsu.edu/etsu-works/550.
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This work reports the use of a head-motion monitoring system to record patient head movements while completing in-home exercises for vestibular rehabilitation therapy. Based upon a dual-axis gyroscope (yaw and pitch, ± 500-degrees/sec maximum), angular head rotations were measured and stored via an on-board memory card. The system enabled the clinician to document exercises at home. Several measurements were recorded in one patient with unilateral vestibular hypofunction: The total time of exercise for the week (118 minutes) was documented and compared with expected weekly exercise time (140 minutes). For gaze stabilization exercises, execution time of 60 sec was expected, and observed times ranged from 75-100 sec. An absence of rest periods between each exercise instead of the recommended one minute rest period was observed. Maximum yaw head velocities from approximately 100-350 degrees/sec were detected. A second subject provided feedback concerning the ease of use of the HAMMS device. This pilot study demonstrates, for the first time, the capability to capture the head-motion “signature” of a patient while completing vestibular rehabilitation exercises in the home and to extract exercise regime parameters and monitor patient adherence. This emerging technology has the potential to greatly improve rehabilitation outcomes for individuals completing in-home gaze stabilization exercises 1 .
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Costa, José Roberto Lima da. "Estudo da função do sistema vestibular em mulheres com disfunção temporomandibular." Universidade de Taubaté, 2011. http://www.bdtd.unitau.br/tedesimplificado/tde_busca/arquivo.php?codArquivo=410.
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Objetivo: Avaliar tipo e frequência de alteração vestibular por meio de vectoeletronistagmografia em indivíduos com Disfunção Temporomandibular (DTM) de origem muscular. Método: Foram incluídos neste estudo 25 pacientes do gênero feminino, com faixa etária de 18 a 44 anos de idade com DTM muscular, classificada de acordo com os critérios do questionário já validado Research Diagnostic Criteria for Temporomandibular Disorders (RDC). Todos os indivíduos foram submetidos à avaliação otoneurológica, composta por anamnese, meatoscopia e vectoeletronistagmografia computadorizada. Resultados: Foram encontrados apenas três sujeitos com alteração na vectoetronistagmografia (alteração do nistagmo pós-calórico). Houve elevada ocorrência de sintomas otoneurológicos, dentre eles: tontura (96%), intolerância a sons altos, cinetose (76%), insônia (72%), plenitudeaural (64%) e zumbido (52%). Os músculos que apresentaram prevalência de dor à palpação foram: tendão do músculo temporal (96%), pterigóideo lateral (96%), masseter médio (92%) e masseter Inferior (68%). Não houve diferença estaticamente significante entre indivíduos com e sem alteração na vectoeletronistagmografia em relação aos principais sintomas otoneurológicos. Também não foi observada diferença estaticamente significante entre mulheres com e sem vertigem com relação à dor à palpação nos músculos estudados. Conclusão: Indivíduos com DTM do tipo muscular apresentaram baixa taxa de alterações vestibulares evidenciadas pelo exame de vectoeletronistagmografia computadorizada, apesar da elevada ocorrência de sintomatologia otoneurológica.Objective: To evaluate the type and frequency of vestibular alteration through vectoelectronystagmography in individuals with temporomandibular disorder (TMD) muscle. Method: The study included 25 female patients, aged 18 to 44 years old with muscular TMD, classified according to the criteria of the questionnaire that has been validated by Research Diagnostic Criteria for Temporomandibular Disorders (RDC). All subjects underwent otoneurologicalavaliation consisting of anamnesis, otoscopyand computerized vectoelectronystagmography. Results: There were only three subjects with altered vectoelectronystagmography (modification of post-caloric nystagmus). There was a high occurrence of otoneurological symptoms, including dizziness (96%), intolerance to loud sounds, motion sickness (76%), insomnia (72%), fullness (64%) and tinnitus (52%). The muscles that had a prevalence of pain on palpation were temporal muscle tendon (96%), lateral pterygoid (96%), the middle portion of masseter (92%) and the lower masseter (68%). There was no statistically significant difference between individuals with and without changes in vectonystagmography on the main otoneurological symptoms.There was also no statistically significant difference between women with and without vertigo with respect to pain on palpation in the muscles studied. Conclusion: Individuals with TMD of muscular type showed a low rate of vestibular disorders revealed by the computerized vectoelectronystagmography despite the high occurrence of otoneurological symptoms.
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Humphrey, Laura Renae. "Modeling the Role of the Foot, Toes, and Vestibular System in Human Balance." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1250218272.
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Merkle, Andrew Charles. "The Implementation of a Photoelectronic Motion Transducer for Measuring the Sub-Micrometer Displacements of Vestibular Bundles." Thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/33170.
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The vestibular system is one of our main organs responsible for the sense of balance. This system is located within the inner ear and contains cells with ciliary bundles. These hair cells are transducers
that convert a mechanical movement, detected by the bundle of cilia extending from their top surface, into an electrochemical signal to be sent to the brain. The bundles vary structurally within the organs
of the inner ear, and this structural difference may play a role in the mechanical properties of each bundle. Analyzing the mechanical properties of the cells will provide information necessary for
understanding the transduction process. In an effort to evaluate one of these properties, cell bundle stiffness, a system was designed to mechanically stimulate the bundles within their physiological range
and then measure the resulting displacement. The mechanical stimulation was the result of a force applied to the tip of a bundle with the end of a glass whisker. The distance the base of the whisker moves
is measured by an extrinsic Fabry-Perot interferometer (EFPI). The magnitude of this movement is compared with the amount the bundle is deflected, detected by a photoelectronic motion transducer (PMT).
Knowing these displacements and the stiffness of the glass whisker, simple kinematics is used to determine the bundle stiffness. System tests were conducted on imitation bundles (whiskers of known stiffness)
and the experimental stiffness differed from the known value by less than 4.5% for every test. These results lead us to conclude the system was in good working order and could be used to conduct tests on
cell bundles. For tissue tests, this work focused on the hair cells located within the utricle, which senses linear accelerations of the head. Within the utricle, we examined two types of hair cells:
non-striolar (medial type II) and striolar. Tests on twelve medial type II cells found bundles ranging in stiffness from 0.26 to 2.62 x 10-5 N/m. Results with striolar bundles provided a range from 2.83 to
27.10 x 10-5 N/m. The results of the preliminary tissue tests lead us to conclude that the average stiffness of the striolar and non-striolar bundles seems to vary by an order of magnitude. This is consistent
with the relative relationship produced through a computer model. However, the model predicted larger stiffness values for both types of cells.Master of Science
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Silverman, Jennifer Mary. "Experimental Measurements of Vestibular Hair Bundle Stiffness in the Red Ear Slider Turtle Utricle." Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/9705.
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The ear is the organ used for hearing and maintaining equilibrium. In the inner ear, the vestibular system is responsible for the sense of balance. The main organs of the vestibular system are the semicircular canals, the saccule, and the utricle. Within each of the vestibular organs, sensory receptors in the form of hair cells detect motion and send a message to the brain for interpretation. Hair cells found in different parts of the inner ear are structurally different and are mechanically specialized to perform different functions. In this study, the linear and torsional stiffnesses were measured for hair cells located in the red ear slider turtle utricle. The system used to measure the stiffnesses was composed of a glass whisker (attached to a pipette) used to produce a force on the tip of the bundle, an extrinsic Fabry-Perot interferometer (EFPI) to measure the displacement of the pipette, and a photoelectronic motion transducer (PMT) to measure the displacement of the bundle. Using the measured values of whisker stiffness, whisker displacement, and bundle displacement, the stiffness of the bundle was calculated using statics. For each bundle tested, the location of the bundle was determined by measuring its position from a landmark in the utricle, the line of polarity reversal, characterized by a 180o change in direction of the hair bundles. Stiffness results showed that the linear stiffness of a bundle increased in the area surrounding the line of polarity reversal, otherwise referred to as the striolar region (average linear stiffness of 2.27 E-04 N/m). The average linear stiffness value of bundles found lateral to the striolar region was 6.30 E-05 N/m and in the region medial to the striolar region was 1.16 E-04 N/m. A wide range of linear stiffnesses were found in hair cells medial to the striolar region. There was no correlation found between the torsional stiffness of a bundle and its position and the height of a bundle and its linear or torsional stiffness. As the force applied to a hair bundle was increased, the measured linear stiffness of the bundle also increased.Master of Science
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Pogson, Jacob M. "Moving Ears and Eyes: Quantifying the Head-Impulse Test in the Clinic." Thesis, The University of Sydney, 2018. http://hdl.handle.net/2123/20935.
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Visual fixation is maintained during a rapid passive ‘head-impulse’ stimulus by the vestibulo-ocular reflex (VOR) while saccades change fixation. This thesis examines these eye movement characteristics with the monocular video head impulse test (vHIT) of the right eye. In eighty healthy controls, the VOR gain was found to depend on analysis method and the stimulus peak velocity, with age affecting only the left posterior and anterior canals. Minuscule compensatory saccades were common towards lateral and posterior canals, but rare towards anterior canals, and became larger and more common in older subjects. In forty subjects before complete unilateral vestibular loss (UVL) for schwannoma, the VOR gains of the lateral and posterior canals of the ipsilesional ear reduced. After surgery, the OFF direction of the remaining ear was reduced for all canals. The dynamic range (ON minus OFF) of the posterior canal was only 39% of the lateral and anterior canals. After surgery, from one week to one year the first compensatory saccade frequency was permanently saturated at unchanged amplitudes, while the second saccade decreased in both measures. Saccade latency was earlier with lower gains. In twenty-two UVL subjects, early saccades occurred at similar frequency, magnitude, and latency with and without visual fixation. However, in eighteen healthy and eight bilateral vestibular loss (BVL) subjects, visual fixation evoked more late compensatory saccades than without fixation. Late saccades in UVL were smaller in magnitude and increased in latency. BVL subjects showed more frequent and larger early and late saccades with fixation. A case-series of twenty-seven subjects after sudden hearing loss with vertigo commonly showed loss of the posterior canal VOR and cochlear function. Audio-vestibular tests cannot distinguish between ischaemic and non-ischaemic causes. In summary, quantification of both the VOR and compensatory saccades are useful for identifying lesions involving each semicircular canal.
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Sun, Bing, and 孫冰. "Vestibular influence on central cardiovascular regulation in the rat: functional and anatomical aspects." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2003. http://hub.hku.hk/bib/B31244774.
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Knox, Craig A. "A model for morphological change in the hominid vestibular system in association with the rise of bipedalism." Virtual Press, 2007. http://liblink.bsu.edu/uhtbin/catkey/1371468.
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This study re-examines the morphological data and conclusions of Spoor, Wood, and Zonneveld concerning the morphology of the vestibular apparatus in relation to locomotor behavior in hominids (1994). The pedal and labyrinthine morphology of early hominid taxa are functionally analyzed for classification as either obligate bipeds or habitual bipeds with primarily arboreal locomotion. The bony labyrinth is investigated since the anatomy of the semicircular canals of the vestibular auditory system can be determined in fossil crania through computed tomographical analysis. It is thought that a relationship exists between semicircular canal size and locomotor behavior. Functionally modern pedal morphology precedes modern vestibular morphology in the fossil record. Complete modern pedal morphology, however, appears concurrently with modern vestibular morphology first at Homo erectus. A comparison of the genes involved in the development of both pedal and labyrinthine morphology was undertaken. It was found that only fibroblast growth factor 8 (FgfS) and sonic hedgehog (Shh) are shared between these systems in the determination of positional information. It is found that the function of Fgf8 in otic induction and in limb bud formation is very different. It is also found that the function of Shh in vestibular and pedal morphogenesis is different. Therefore, it is unlikely for alteration in the function or in the expression of either gene to result in the observed differences in pedal and vestibular morphology between early hominid taxa: Australopithecus afarensis, Australopithecus africanus, Homo habilis; and Homo erectus. My examination of the data on the timing of changes in pedal morphology rejects Spoor, Wood, and Zonneveld's conclusion. Moreover I find no gene mutation which could account for simultaneous change in the shape of the semicircular canals and the proportions of the metatarsals and pedal phalanges. Instead, it is postulated that the change to modern vestibular morphology at Homo erectus is in response to a concurrent enlargement in cranial capacity. It is also postulated that persistence of panid vestibular morphology in the semicircular canals of hominid taxa: Australopithecus afarensis, Australopithecus africanus, and Homo habilis is a functionally neutral trait in regard to bipedal locomotor capability.Department of Anthropology
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Le, gall Anne. "Influence de la graviception vestibulaire sur le développement et les fonctions cognitivo-motrices à l'âge adulte : étude longitudinale chez un modèle murin vestibulo-déficient." Thesis, Normandie, 2017. http://www.theses.fr/2017NORMC421.
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La gravité terrestre est une contrainte mécanique fondamentale exercée sur les organismes vivants et contre laquelle nous avons adapté nos stratégies de posture et de locomotion ainsi que toutes les régulations métaboliques et cardiovasculaires. Outre le stimulus mécanique direct, la gravité est mesurée par l'organe vestibulaire, premier système sensoriel à émerger chez les protochordés il y a environ 500 millions d'années, aussi précocement que le système visuel. Le système vestibulaire a alors été asservi aux fonctions d'équilibre et de stabilisation du regard, par des réflexes posturaux et oculaires, fonctions récemment enrichies d’un rôle clé dans la cognition spatiale et sociale chez l’adulte. Ses capacités d’encodage des mouvements de la tête, des accélérations du corps et de la gravité terrestre font de ce système un acteur majeur dans la perception de la verticalité, la navigation, l’orientation et la mémorisation spatiale. Nous avons émis l'hypothèse que la perception sensorielle vestibulaire de la gravité via les otolithes pourrait jouer un rôle crucial non seulement chez l’adulte mais également dans les premières étapes du développement des fonctions sensorimotrices et cognitives. Pour la première fois, nous avons étudié un modèle de souris original (souris Head-tilt, B6Ei.GL-Nox3Het / J) présentant une absence congénitale sélective de gravisenseurs vestibulaires. Les souris présentaient un retard dans l'acquisition des réflexes sensorimoteurs, des capacités d’orientation spatiale par guidage olfactif, d'une communication mère-petits par ultrasons alors que les soins maternels étaient normaux. Un retard dans la locomotion et des troubles hyperactifs avec stéréotypies ont également été montré. Nous démontrons ainsi que le développement des individus sur Terre possède une période critique dépendante de la perception sensorielle vestibulaire de la gravité, au moins entre les jours post-nataux 6 à 10 chez les rongeurs. Les informations otolithiques jouent également un rôle clé chez l’adulte dans les fonctions motrices, les processus mnésiques spatiaux et non spatiaux et dans la régulation émotionnelle. Une corrélation entre ces troubles et le retard développemental a été mis en évidence. Nous travaillons actuellement sur les effets de stimulations sensorielles précoces sur le développement et les fonctions adultes chez la souris Het ainsi que sur la caractérisation structurale et fonctionnelle au niveau cérébral des atteintes développementales et comportementales observées. Les observations chez les souris Het corroborent les symptômes rapportés chez les enfants vestibulo-déficients, soutenant le besoin d'un meilleur dépistage des maladies vestibulaires pendant l'enfance. De manière intéressante, les symptômes de ces souris correspondent à ceux présentés par des modèles murins validés d'autisme et réactualiseraient l’importance de la graviception vestibulaire dans la physiopathologie et la thérapie des troubles du spectre autistique (TSA) et autres maladies neurodégénératives au cours du développementEarth’s gravity is a fundamental mechanical constraint for living organisms against which we have adapted our strategies of posture and locomotion as well as all metabolic and cardiovascular regulations. Beyond the mechanical stimulus, the vestibular organ is the first sensory system to emerge in protochordates about 500 million years ago, as early as the visual system, encoding the gravity strength into the brain. The vestibular system has since then been devoted to balance and gaze stabilization supported by postural and ocular reflexes, recently fortified with a key role in spatial and social cognition in adults. Its encoding abilities of head movements, body accelerations and Earth's gravity make this system a major player in the perception of verticality, navigation, orientation and spatial memorization. We have hypothesized that vestibular sensory perception of gravity might play a crucial role not only in adults, but also during the first stages of development in both sensorimotor and cognitive functions. For the first time, we have investigated an original mouse model (Head-Tilt mice, B6Ei.GL-Nox3Het/J) with selective congenital absence of vestibular gravisensors. Our data highlights that mouse pups suffered from a delay in the acquisition of sensorimotor reflexes, spatial olfactive guidance, path integration and ultrasonic communication while maternal care remained normal. In addition, a delay in locomotor development and the appearance of were observed during the late stage of development. We demonstrate that development on Earth has a critical period dependent on the vestibular sensory perception of gravity, at least between postnatal days 6 to 10 in rodents. We have shown that otolithic information plays a key role in the adult motor functions, spatial and non-spatial memory processes, reference frames choice but also in emotional regulation. These disorders have been correlated with early developmental delay. We are currently working on the effects of early sensory stimulation on development and adult functions in our Het mouse model as well as on the structural and functional characterization at the cerebral level of observed developmental and behavioral impairments. Observations in Het mice corroborate with symptoms reported in vestibulo-deficient children, supporting the need for better screening of vestibular diseases during childhood. Remarkably, the symptoms of our vestibulo-congenital deficient mice investigated here matched with the profile of validated mouse models of autism and re-update the significance of vestibular graviception in the physiopathology and therapy of autism spectrum disorders during its development
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Justina, Hellen Mathei Della. "Variabilidade da atividades cerebral em resposta a estímulos vestibular e ocolomotor avaliada por fMRI." Universidade de São Paulo, 2005. http://www.teses.usp.br/teses/disponiveis/59/59135/tde-14092007-143548/.
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A avaliação da variabilidade inter-individual da atividade funcional é de grande importância na utilização da ressonância magnética funcional (fMRI) no contexto clínico. O objetivo principal desse estudo é analisar a variabilidade da ativação cerebral dos sistemas vestibular e oculomotor, através da fMRI em resposta à estimulação optocinética horizontal e aos movimentos de rastreio e sacade dos olhos. Para isso, imagens por ressonância magnética foram obtidas de vinte e três voluntários assintomáticos (treze para o estudo optocinético e dez para os estudos rastreio e sacade) em um scanner de 1.5 T Siemens (Magneton Vision) com seqüências do tipo EPI-BOLD. Os mapas estatísticos foram obtidos no programa Brain Voyager, utilizando o método Modelo Geral Linear. Encontramos ativação significante no córtex visual primário, ao longo do giro occipital médio e inferior, no giro temporal médio, superior e inferior, no giro pós- e pré-central, ao longo do giro frontal inferior, superior e médio, no giro supramarginal, no lobo parietal superior e inferior, na ínsula e no cíngulo anterior e posterior. Grupos de atividade também foram encontrados em estruturas subcorticais (putamen, globo pálido, corpo caloso e tálamo), além do cerebelo. A análise da freqüência de ativação revelou uma alta variabilidade entre voluntários. Contudo, as regiões com maior freqüência de ativação foram as áreas frontais e a área que compreende o giro temporal médio e médio superior. Utilizamos dois métodos para a análise dos índices de lateralização, o primeiro admite um valor estatístico fixo e o segundo leva em consideração a dependência do limiar estatístico com o número de pixels ativados, o segundo método mostrou-se mais confiável. Os índices mostraram uma dominância do hemisfério direito para o estudo optocinético. Já, para os estudos rastreio e sacade, não verificamos essa dominância. Esse estudo permitiu a caracterização das mais freqüentemente áreas envolvidas nas tarefas de estimulação optocinética e dos movimentos de rastreio e sacade dos olhos. A combinação dessas tarefas constitui uma grande ferramenta para determinar a lateralização dessas funções e mapear as maiores áreas envolvidas nos sistemas oculomotor e vestibular.Assessing inter-variability of functional activations is of practical importance in the use of functional magnetic resonance imaging (fMRI) in clinical context. The main objective of this study is to analyze the variability of cerebral activation of the vestibular and oculomotor systems through an optokinetic horizontal, a pursuit and saccadic eye movement stimulations by means of fMRI. For this, images of magnetic resonance were acquired of twenty and three asymptomatic volunteers (thirteen for the optokinetic study and ten for the pursuit and saccade stimulations) in scanner of 1.5 T Siemens (Magneton Vision) with EPI-BOLD fMRI sequences. The statistical maps were analyzed in Brain Voyager software, using the method General Linear Model. We find significant activation in primary visual cortex, in middle and inferior occipital gyrus, in middle, superior and inferior temporal gyrus, in postcentral and precentral gyrus, in middle, inferior and superior frontal gyrus, in supramarginal gyrus, in superior and inferior parietal lobule, in insula and in anterior and posterior cingulate gyrus. Groups of activity had been also found in subcorticals structures (putamen, globus pallidus, corpus callosum and thalamus), beyond the cerebellum. The analysis of the activation frequency displays a high variability between volunteers. However, the most frequently activation regions were localized in areas frontals and in regions comprehending the middle and medial superior temporal gyrus. We use two methods for the analysis of the laterality index, the first admits a fixed statistical value and the second takes in consideration the dependence of the statistical threshold within the activated number of pixels, the second method revealed more reliability. The indices had shown a right hemisphere dominance for the optokinetic study but, for the pursuit and saccade stimulations, we do not verify this dominance. Our study allowed the characterization of the most frequently involved foci in tasks of optokinetic and pursuit and saccade eye movement stimulations. The combination of these tasks constitutes a suitable tool for determine the lateralization of these functions and for mapping major areas involved in the oculomotor and vestibular systems.
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Cogo, Lícia Assunção. "A INFLUÊNCIA DO ORGANOFOSFORADO CLORPIRIFÓS NO SISTEMA VESTIBULAR DE COBAIAS." Universidade Federal de Santa Maria, 2013. http://repositorio.ufsm.br/handle/1/6552.
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Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorSome chemicals have caused much damage to humans and the environment. Among these substances are chemical compounds like pesticides, often considered responsible for poisoning the workers, making it a public health problem. The aim of this study was to verify whether the organophosphate chlorpyrifos was influential in the vestibular system of guinea pigs in acute exposure. This was an experimental research. The research used 18 albino guinea pigs of the species Cavia porcellus, divided into three groups, with group I control the other, using distilled water and containing five animals. In Group II, six animals were administered 0.5 mg / kg / day of pesticide chlorpyrifos and group III, with seven animals at a dose of 1mg/kg/day of the same pesticide. The three groups were under experiment for 10 days. For analysis of the results was performed functional analysis of the vestibular system by electronystagmography (caloric test - with ice water) and histopathological analysis by scanning electron microscopy. The results showed no statistically significant difference for the variable frequency of appearance of nystagmus and angular velocity of the slow component in electronystagmography, and the number of ciliary tufts histologically by scanning electron microscopy. It was concluded that the organophosphate chlorpyrifos did not cause damage to the vestibular system of the guinea pigs at the doses tested in acute exposure.
Algumas substâncias químicas têm causado muitos danos ao ser humano e ao meio ambiente. Dentre estas substâncias encontram-se os compostos químicos do tipo agrotóxicos, frequentemente considerados como responsáveis por intoxicações a trabalhadores, tornando isto um problema de saúde pública. O objetivo geral deste estudo consistiu em verificar se o organofosforado clorpirifós teve influência no sistema vestibular de cobaias em exposição aguda. Tratou-se de uma pesquisa experimental. A pesquisa utilizou 18 cobaias albinas da espécie Cavia porcellus, divididas em três grupos; sendo o grupo I o controle dos demais, utilizando água destilada e contendo cinco animais. No grupo II, com seis animais, foi administrada a dose de 0,5mg/kg/dia de agrotóxico clorpirifós e no grupo III, com sete animais a dose de 1mg/kg/dia do mesmo agrotóxico. Os três grupos estiveram sob experimento durante 10 dias. Para análise dos resultados foi realizada a análise funcional do sistema vestibular através da eletronistagmografia (prova calórica com água gelada) e a análise histopatológica através da microscopia eletrônica de varredura. Os resultados não demonstraram diferença estatística significante para as variáveis frequência de aparecimento de nistagmo e velocidade angular da componente lenta na eletronistagmografia; e no número de tufos ciliares na análise histopatológica por microscopia eletrônica de varredura. Concluiu-se que o organofosforado clorpirifós não ocasionou dano ao sistema vestibular das cobaias nas doses testadas em exposição aguda.
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McElhinney, Sarah-Anne. "A comparison of ocular and cervical vestibular evoked myogenic potentials in the evaluation of different stages of clinically certain Ménière’s disease." Thesis, University of Canterbury. Department of Communication Disorders, 2009. http://hdl.handle.net/10092/3217.
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Cervical vestibular evoked myogenic potential (cVEMP) testing is widely used in the assessment of vestibular disorders in clinical practice (Welgampola & Colebatch, 2003). Ocular vestibular evoked myogenic potentials (oVEMPs) are similar to the cervical VEMPs in that the vestibular system is also stimulated by a loud sound. The difference is that the response is measured on the inferior oblique muscle of the eye as opposed to the sternocleidomastoid muscle (SCM) of the neck (Chihara, Iwasaki, Ushio, & Murofushi, 2007). The current study compares the standard cervical VEMP to the ocular VEMP in both control subjects and participants with “clinically certain” Ménière’s disease. By investigating cervical VEMPs in comparison to ocular VEMPs we aimed to improve the ability to stage and diagnose Ménière’s disease using the ocular VEMP. 22 control participants and 19 participants with confirmed unilateral Ménière’s disease took part in the study. The peak latency and amplitudes of the ocular and cervical VEMP tests were recorded and analysed. In addition, the background electromyographic (EMG) activity of both the inferior oblique and sternocleidomastoid muscles was recorded throughout testing. A questionnaire was also distributed to all participants to compare the relative difficulty of the VEMP tests. Statistical analysis using the paired t-test, standard t-test and the one-way ANOVA on ranks test was applied to determine a difference between the control and patient groups for both the ocular and cervical VEMP tests. Overall, the threshold and IAD ratio measures did not produce any significant results when sound was presented to the affected ear for the cervical and ocular VEMP tests. A significant reduction in amplitude of the VEMPs from the Ménière’s groups was found compared to the control groups for the ocular the cervical VEMPs. Overall, an increase in P2 and N3 latency of the ocular VEMP response in Ménière’s patients was determined. Results from the questionnaire suggest that the ocular VEMP test was more tolerable to the cervical VEMP test in this current study. Furthermore, statistical analyses revealed no significant differences in EMG level between the control and Ménière’s group for both the ocular and cervical VEMP data. Overall, results suggest that both the cervical and ocular VEMP tests provide information regarding the integrity of the saccule, owing to the abnormal VEMP findings in the participants with Ménière’s disease. In addition, this study provides evidence that the ocular VEMP is as useful a tool in diagnosing Ménière’s disease as the cervical VEMP.
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Deroualle, Diane. "Informations vestibulaires et prise de perspective : approches comportementales, cliniques et electrophysiologiques." Thesis, Aix-Marseille, 2017. http://www.theses.fr/2017AIXM0206/document.
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Ce travail a pour but de décrire les relations réciproques entre prise de perspective et informations vestibulaires. Une étude chez des patients avec un déficit vestibulaire bilatéral ancien et des sujets contrôles a montré que l’ancrage du soi sur le corps et la simulation implicite de la perspective visuo-spatiale d’autrui étaient similaires chez les deux groupes. Ainsi, une perte vestibulaire ancienne n’entraînerait pas de conflits multisensoriels, connus pour évoquer un sentiment de perspective désincarnée chez des patients avec des déficits vestibulaires aigus. Une étude chez des volontaires sains a combiné des stimulations vestibulaires naturelles sur fauteuil rotatoire à des tâches de prise de perspective dans un environnement virtuel embarqué. Les temps de prise de perspective étaient modulés en fonction de la direction de la rotation. Cette influence n’était pas présente pour la rotation mentale d’objets 3D. La contribution vestibulaire canalaire modulerait donc spécifiquement les rotations mentales du point de vue. Enfin, les modulations cognitives du traitement des informations vestibulaires ont été analysées par l’enregistrement de potentiels évoqués myogéniques vestibulaires sur les muscles sternocléidomastoïdiens et trapèzes. L’amplitude des potentiels évoqués était significativement modulée par l’angle séparant le point de vue du participant et celui d’un avatar distant. Nos travaux théoriques et les résultats de cette série d’expériences démontrent la contribution des informations vestibulaires à la prise de perspective visuo-spatialeThis thesis aims at describing the reciprocal relations between perspective taking and the vestibular system. A study in patients with bilateral vestibular deficits and controls showed that the anchoring of the self to the body and implicit visuo-spatial perspective taking were similar in both groups. Our negative findings offer insight into the multisensory mechanisms of embodiment: only acute peripheral vestibular disorders and neurological disorders in vestibular brain areas may evoke disembodied experiences. A second study, combined natural vestibular stimulation on a rotatory chair with virtual reality to test how vestibular signals are processed to simulate the view point of a distant avatar. While they were rotated, participants tossed a ball to a virtual character from the view point of a distant avatar. Our results showed that participants were faster when their physical body rotated in the same direction as the mental rotation needed to take the avatar's viewpoint. Altogether, these data indicate that vestibular signals have a direction-specific influence on visuo-spatial perspective taking, but not a general effect on mental imagery. Finally, cognitive modulations of vestibular information processing were analyzed by recording vestibular-evoked myogenic potentials on the sternocleidomastoid and trapeze muscles. The amplitude of evoked potentials was significantly modulated by the angle separating the participant’s viewpoint to that of a distant avatar. To conclude, our theoretical work, together with results from this series of experiments, demonstrate the contribution of vestibular information to visuo-spatial perspective taking
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Jones, Gareth Paul. "Acoustic sensitivity of the vestibular system and mechanical analysis of the tectorial membrane in mammals." Thesis, University of Sussex, 2012. http://sro.sussex.ac.uk/id/eprint/38740/.
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This thesis cover two separate topics related to the function of the mammalian inner ear. Acoustic sensitivity of the vestibular system. Data are presented showing facilitation of the auditory startle response by tones outside the range of the mouse cochlea. The sensation of these low frequency tones is demonstrated to be mediated via the acoustically sensitive sacculus of the vestibular system by data collected from Nox3-/- mice. These mice lack the otoconia of the vestibular system and, unlike the wild-type mice, only show facilitation to tones within the range of the mouse cochlea, and not in response to tones <4 kHz. The mechanical properties of the tectorial membrane (TM). The mechanical properties of the TM are investigated using a laser interferometer-based method for tracking the longitudinal propagation of a radially shearing travelling wave in segments of TM isolated from the basal and apical regions of the wild-type cochlea. The properties of these travelling waves (wave propagation velocity and wave amplitude decay) are tracked over a range of stimulus frequencies (1-20 kHz). The viscoelastic properties, shear storage modulus (G') and shear viscosity (η), are estimated over this frequency range and are found to be lower in the apical TM segments compared to the basal TM segments, indicating the apical region of the TM is less stiff than the basal region. These data are compared to data collected from TM segments isolated from the basal cochlear region of three mutant groups, each lacking expression of TM-specific proteins; α-tectorin (TectaY1870C/+), β-tectorin (Tectb-/-) and otoancorin (OtoaEGFP/EGFP), using the same laser interferometer-based method. The viscoelastic properties are estimated for each of the mutants and indicate varying degrees of loss of structural integrity in their respective TM segments. Reflective difference between the wild-types and mutants are also observed and compared.
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Jin, Ying. "Neuronal survival and axonal regeneration of the lateral vestibular nucleus in rats after spinal cord injury /." Hong Kong : University of Hong Kong, 1998. http://sunzi.lib.hku.hk/hkuto/record.jsp?B19918847.
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Dutheil, Sophie. "Une nouvelle zone de neurogenèse réactionnelle et fonctionnelle chez le mammifère adulte : les noyaux vestibulaires - mise en évidence et implication fonctionnelle dans différents modèles de déafférentation vestibulaire." Thesis, Aix-Marseille, 2012. http://www.theses.fr/2012AIXM4752/document.
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Seules deux structures du système nerveux central adulte, la zone sous-granulaire et la zone sous-ventriculaire, produisent continuellement de nouveaux neurones et sont considérées comme neurogènes. En dehors de ces zones délimitées, le tissu nerveux ne possède pas de telles facultés. Leurs influences anti-neurogènes peuvent cependant être mises entre parenthèses dans certaines conditions. Cela se produit après neurectomie vestibulaire unilatérale (NVU) chez le chat adulte ; en effet, des études immunohistochimiques et comportementales nous ont permis de découvrir l'existence d'une neurogenèse réactionnelle de type GABAergique dans les noyaux vestibulaires désafférentés situés dans le tronc cérébral. Nos résultats témoignent de l'implication fonctionnelle de cette prolifération cellulaire dans la restauration des fonctions posturo-locomotrices suite à une NVU. Nous avons également mis en évidence que les caractéristiques et l'intensité de la désafférentation vestibulaire déterminent, non seulement, le décours temporel de la restauration des fonctions vestibulaires, mais aussi les différents mécanismes cellulaires post-lésionnels et le potentiel neurogène des noyaux vestibulaires. En outre, nous avons démontré que l'activation ou le blocage des récepteurs GABA de type A influence d'une part, les différentes étapes de la neurogenèse réactionnelle dans les noyaux vestibulaires, et détermine d'autre part le décours de la récupération comportementale des animaux. Ainsi, le système GABAergique joue-t-il un rôle important dans la régulation de la neurogenèse induite après NVU et de sa fonctionnalitéOnly two structures of the adult central nervous system: the subgranular zone and the subventricular zone, produce continuously new neurons and are considered as neurogenic. Outside these two delimited areas, nervous tissue does not have such faculties. The anti-neurogenic influences can however be removed under specific conditions. That is what happens after unilateral vestibular neurectomy (UVN) in the adult cat: behavioral and immunohistochemical studies have demonstrated the existence of a reactive GABAergic neurogenesis in the deafferented vestibular nuclei located in the brainstem. Our results demonstrate the functional role of the vestibular cell proliferation in the postural locomotor function recovery after UVN. We also demonstrated that characteristics and intensity of the vestibular lesion, not only determine the time course of recovery of vestibular function, but also the post-lesional cellular mechanisms and the neurogenic potential occurring in the vestibular nuclei. In addition, we showed that activation or blockade of GABA type A receptors influences the different steps of neurogenesis in the vestibular nuclei, and also determines the time course of behavioral recovery. Thus, the GABAergic system influences reactive neurogenesis that is benefic for vestibular compensation process. Finally, the results of a recent study demonstrated that vestibular-hippocampal relations exist, and that stress induced by vestibular deafferentation can modulate adult neurogenesis in both the vestibular nuclei and the dentate gyrus in the adult cat
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Parzefall, Birgit. "PCR-based investigation of the presence of herpesvirus in the peripheral vestibular system in cats and dogs." Diss., lmu, 2010. http://nbn-resolving.de/urn:nbn:de:bvb:19-124009.
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Jin, Ying, and 金瑩. "Neuronal survival and axonal regeneration of the lateral vestibular nucleus in rats after spinal cord injury." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1998. http://hub.hku.hk/bib/B31237113.
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Keywan, Aram [Verfasser], and Klaus [Akademischer Betreuer] Jahn. "Subliminal stochastic electrical stimulation of the vestibular system: effects on posture and perception / Aram Keywan ; Betreuer: Klaus Jahn." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2020. http://d-nb.info/1225682568/34.
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Cheong, Michael Alexander. "Genetic and physical mapping of the mouse deafness gene bronx waltzer (bv) and its effect on the vestibular system." Thesis, University of Nottingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.312200.
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Greguske, Erin A. "Vestibular Damage and Repair in Chronic Ototoxicity: Cellular Stages, Physiological Deficits and Molecular Mechanisms." Doctoral thesis, Universitat de Barcelona, 2019. http://hdl.handle.net/10803/668022.
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Progressive ototoxicity of the inner ear is prevalent in patients administered aminoglycoside antibiotics with little understanding of how this damage occurs and to what extent it can be recovered. Numerous in vitro and in vivo studies using acute methods have been completed to demonstrate various types of damage in vestibular and auditory tissue, including hair cell damage that results in apoptosis or necrosis, excitotoxic damage, and/or degeneration of their afferents. However, progressive damage has only just recently been studied utilizing a sub-chronic exposure rat model; this model takes into account the progressive exposure mirrored in aminoglycoside administration that is not implied in acute experimentation. With this in mind, the sub-chronic exposure model was adapted for a new mouse model to characterize the progressive damage taking place in vestibular sensory epithelia and ganglia, along with a preliminary characterization in cochlear sensory epithelia. Mice were exposed to 30 mM IDPN (3,3’- iminodipropionitrile) in regular drinking water for 8 weeks, and monitored for vestibular deficits using an established test battery; auditory deficits were recorded using auditory brainstem response (ABR) measurements. Various techniques for identifying functional, histological (scanning/transmission electron microscopy; immunoconfocal), and molecular (mRNA; protein) data were utilized to study alterations in the vestibular and auditory tissues after sub-chronic intoxication. In the vestibular tissue, SEM/TEM imaging demonstrated progressive damage with the loss of calyceal junctions between type I hair cells and their calyx afferents, the fragmentation and retraction of the afferents, stereociliary bundle coalescence, and the unique mechanism of hair cell extrusion, where the cell is ejected from the epithelia into the endolymphatic cavity. Immunoconfocal and qRT-PCR data demonstrated a loss of caspr1 and tenascin-c in the calyceal junctions of type I hair cells and their afferents. A loss of active synapses between hair cells and their afferents was also noted, where active synapses were defined by the pre-synaptic ribeye of the hair cells and the post-synaptic GluA2 receptor of the afferents. Synaptic scaffolding protein expression was upregulated (PSD95, Homer1), which translated into an increase in the protein level (PSD95), likely for hair cell-afferent synapse stabilization and compensation. Progressive damage was noted to be at least partially or completely recoverable up until stereocilia coalescence of the hair cells. Finally, the expression of numerous scaffolding and signaling proteins were shown to be downregulated (qRT-PCR; RNAseq) during the exposure in the vestibular epithelium and ganglion, leading to the hypothesis of a depression in cell-cell adhesion between hair cells and their afferents and a depression in afferent signaling, resulting in an overall depressed system. In the cochlea, profound hearing loss was observed in a tonotopic pattern during the exposure; higher frequencies were affected first with longer exposure times affecting lower frequencies. Outer hair cells were lost tonotopically due to prolonged exposure, followed by active synapse loss of the inner hair cells. Those intoxicated for the first two weeks demonstrated a capacity for recovery before any outer hair cell or active synapse losses were seen. A sub-chronic ototoxic IDPN model demonstrates the progressive damage of the inner ear, allowing for the study of this damage and its potential for recoverability, gaining a clearer understanding of the mechanisms affecting the tissues.La ototoxicidad progresiva del oído interno prevalece en los pacientes a los que se les administraron antibióticos aminoglucósidos con poca comprensión de cómo se produce este daño y hasta qué punto se puede recuperar. Se han completado numerosos estudios in vitro e in vivo para demostrar diversos tipos de daño en el tejido vestibular y auditivo; recientemente, se ha estudiado el daño progresivo utilizando un modelo de intoxicación subcrónica en rata. Este modelo tiene en cuenta la exposición progresiva reflejada en la administración de aminoglucósidos que no está implícita en los experimentos agudos. El modelo de intoxicación subcrónica se adaptó a un nuevo modelo de ratón para describir como se caracteriza el daño progresivo que se produce en los epitelios sensoriales vestibulares y los ganglios, junto con una caracterización preliminar en los epitelios sensoriales cocleares. Los ratones se expusieron a IDPN 30 mM (3,3'-iminodipropionitrilo) en agua potable normal durante 8 semanas y se observaron los déficits vestibulares utilizando una batería de pruebas establecida; los déficits auditivos se registraron utilizando medidas de respuesta auditiva del tronco cerebral. Se utilizaron diversas técnicas para estudiar las alteraciones en los tejidos vestibular y auditivo después de una intoxicación subcrónica. En el tejido vestibular, demostró un daño progresivo con la pérdida de las uniones calíceas entre las células ciliadas tipo I y sus aferentes del cáliz, la fragmentación y retracción de los aferentes, la coalescencia estereociliar y el mecanismo único de extrusión de células ciliadas. También se observó una pérdida de sinapsis activas y se demostró que la expresión de numerosas proteínas de andamiaje y señalización estaba regulada a la baja durante la intoxicación. En la cóclea, se observó una pérdida auditiva profunda en un patrón tonotópico durante la exposición y las células ciliadas externas se perdieron tonotópicamente debido a la exposición prolongada, seguida de la pérdida activa de sinapsis de las células ciliadas internas. Un modelo de IDPN ototóxico subcrónico demuestra el daño progresivo del oído interno, lo que permite el estudio de este daño y su potencial de recuperación, obteniendo una comprensión más clara de los mecanismos que afectan a los tejidos.
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Pospisil, Eric Robert. "Understanding human balance through applied robotics : exploring the roles of ankle motion and the vestibular system in maintaining standing balance." Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/50866.
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This thesis details the implementation and application of a robotic system for investigating the role of somatosensory feedback and the human vestibular apparatus in maintaining standing balance.
A 6 degree-of-freedom Stewart platform is employed to explore the human balance system in ways not possible during normal standing conditions. This robotic system, RISER (Robot for Interactive Sensory Engagement and Rehabilitation), uses a physics-based model to simulate of a variety of balance conditions for participants while they are secured to the system, making it possible to modify or isolate aspects of the balance control system for study.
The first study explores the role of somatosensory feedback using a robotic “ankle-tilt” platform, which was designed and implemented on the RISER system. The new platform enables independent manipulation of the ankles during balance simulations. Results demonstrate that providing accurate somatosensory feedback plays a significant role in improving balance control during standing simulations through reduction of sway amplitude and smoother motion during deliberate sway. The addition and validation of this platform opens new avenues for research involving incorrect, delayed, or partial somatosensory feedback, to study the effects of varying these parameters on balance performance.
In the second set of studies, a new technique is developed for investigating the gains and delays of the vestibular organs, employing the ankle-tilt platform. These studies utilized sinusoidal Galvanic Vestibular Stimulation (GVS) to generate an isolated vestibular error signal, producing sensations of motion. The RISER system is used to relate the response to GVS with the response to physical motions. The author investigates the perception and reflex responses to GVS using the RISER system, and demonstrates that sinusoidal GVS and rotation can be combined to produce superimposed perceptions or reflex responses. The author also compares the relationships frequency-dependant phase relationship between GVS and rotation, and finds that they do not conform to prior model expectations. Possible reasons for these discrepancies are examined, and repercussions on the existing understanding of the human balance model are considered.Applied Science, Faculty of
Mechanical Engineering, Department of
Graduate
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Brand?o, Adriana Jussara de Oliveira. "O complexo nuclear vestibular do sagui (callithrix jacchus): caracteriza??o citoarquitet?nica e neuroqu?mica." Universidade Federal do Rio Grande do Norte, 2010. http://repositorio.ufrn.br:8080/jspui/handle/123456789/16683.
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To the vertebrates, maintain body balance against the gravitational field and be able to orient themselves in the environment are fundamental aspects for survival, in which the participation of vestibular system is essential. As part of this system, the vestibular nuclear complex is the first central station that, by integrating many information (visual, proprioceptive), and the vestibular, assumes the lead role in maintaining balance. In this study, the vestibular nuclear complex was evaluated in relation to its cytoarchitecture and neurochemical content of cells and axon terminals, through the techniques of Nissl staining and immunohistochemistry for neuronal specific nuclear protein (NeuN), glutamate (Glu), substance P (SP), choline acetyltransferase (ChAT) (enzyme that synthesizes acetylcholine-Ach) and glutamic acid decarboxylase (GAD) (enzyme that synthesizes gamma-amino butyric acid-GABA). The common marmoset (Callithrix jacchus) was used as experimental animal, which is a small primate native from the Atlantic Forest in the Brazilian Northeast. As results, the Nissl technique, complemented by immunohistochemistry for NeuN allowed to delineate the vestibular nucleus superior, lateral, medial and inferior (or descending) in the brain of the common marmoset. Neurons and terminals immunoreactive to Glu and ChAT and only immunoreactive terminals to SP and GAD were seen in all nuclei, although in varying density. This study confirms the presence in the vestibular nuclei of the common marmoset, of Glu and SP in terminals, probably from the first order neurons of vestibular ganglion, and of GABA in terminals, presumably from Purkinge cells of the cerebellum. Second-order neurons of the vestibular nuclei seem to use Glu and Ach as neurotransmitters, judging by their expressive presence in the cell bodies of these nuclei in common marmosets, as reported in other species
Para os vertebrados, manter o equil?brio corporal contra o campo gravitacional e ser capaz de orientar-se no ambiente s?o aspectos fundamentais para a sobreviv?ncia, nos quais ? essencial a participa??o do sistema vestibular. Como parte deste sistema, o complexo nuclear vestibular ? a primeira esta??o central que, ao integrar v?rias informa??es (visual, proprioceptiva), al?m da vestibular, assume o papel principal na manuten??o do equil?brio. Neste estudo, o complexo nuclear vestibular do sagui foi avaliado com rela??o a sua citoarquitetura e conte?do neuroqu?mico de c?lulas e terminais ax?nicos, atrav?s das t?cnicas de colora??o de Nissl e imuno-histoqu?mica para prote?na neuronal nuclear espec?fica (NeuN), glutamato (Glu), subst?ncia P (SP), colina acetiltransferase (ChAT) (enzima de s?ntese da acetilcolina-Ach), e descarboxilase do ?cido glut?mico (GAD) (enzima de s?ntese do ?cido gama-amino-but?rico-GABA). Foi utilizado como animal experimental o sagui (Callithrix jacchus), um pequeno primata nativo da Mata Atl?ntica do Nordeste Brasileiro. Como resultados, a t?cnica de Nissl, complementada pela imuno-histoqu?mica para NeuN, permitiu delinear os n?cleos vestibulares superior, lateral, medial e inferior (ou descendente) no enc?falo do sagui. Neur?nios e terminais imunorreativos a Glu e ChAT e apenas terminais imunorreativos a SP e GAD foram vistos em todos os n?cleos, embora em densidade vari?vel. Este trabalho confirma a presen?a nos n?cleos vestibulares do sagui, de Glu e SP em terminais, provavelmente provenientes dos neur?nios de primeira ordem do g?nglio vestibular, e de GABA em terminais, supostamente provenientes das c?lulas de Purkinge do cerebelo. Neur?nios de segunda ordem dos n?cleos vestibulares parecem usar Glu e Ach como neurotransmissores, a julgar pela sua expressiva presen?a em peric?rios destes n?cleos no sag?i, como relatado em outras esp?cies
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Hornby, Rene. "A multiple test battery approach during the assessment of the auditory nervous system of patients with multiple sclerosis." Pretoria : [s.n.], 2002. http://upetd.up.ac.za/thesis/available/etd-07222005-155411.
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Kuldavletova, Olga. "L'intégration multisensorielle fonctionnelle et la plasticité des réflexes vestibulaires Vestibulo-sympathetic Reflex in Patients With Bilateral Vestibular Loss Influence of Graviceptor Stimulation Initiated by Off-Vertical Axis Rotation on Ventilation Effect of self-motion perception on autonomic control Vestibulo-Ocular Responses, Visual Field Dependence, and Motion Sickness in Aerobatic Pilots." Thesis, Normandie, 2020. http://www.theses.fr/2020NORMC405.
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L’objectif de ce travail de thèse était d’évaluer le rôle du système vestibulaire dans l’homéostasie en relation avec l’orientation.Nous avons évalué les réponses vestibulaires (1) dans une population normale pour évaluer le niveau d’implication des différents systèmes sensoriels dans la régulation cardiovasculaire et respiratoire et (2) dans des populations présentant des informations vestibulaires perturbées : soit des patients avec un déficit vestibulaire bilatéral soit des pilotes de voltiges aérienne.Les résultats indiquent que les informations vestibulaires et celles des gravicepteurs du tronc s’associent pour réguler la réponse respiratoire lors de la rotation à axe incliné selon la gravité (RAIG). La contribution respective des récepteurs vestibulaires et des gravicepteurs dans cette réponse varie en fonction des individus. Une autre étude a testé l’hypothèse selon laquelle la modulation de la réponse cardio-vasculaire par le système vestibulaire peut être influencée par les informations visuelles pendant la RAIG. Les résultats préliminaires de cette étude ont montré que la stimulation RAIG a un effet sur les valeurs moyennes des paramètres cardio-vasculaires. L'effet modulateur de la RAIG sur la pression artérielle a également été démontré. Cette modulation de réponse, et plus particulièrement la phase, variait entre les individus, ce qui peut indiquer la nature neuronale de la modulation observée. Un effet de la stimulation visuelle sur la modulation semble être également présent, mais une analyse plus approfondie est nécessaire pour confirmer ce résultat. Dans une autre étude, il s’est avéré que des patients présentant une déficience vestibulaire bilatérale avaient la même réponse cardio-vasculaire aux changements de position de la tête pendant le protocole « head down neck flexion » que les sujets témoins. Ces résultats indiquent que cette reconstruction du réflexe vestibulo-sympathique semble provenir de sources sensorielles autres que labyrinthiques. Enfin, nous avons étudié les pilotes de voltige aérienne comme modèle de sujets subissant des stimulations vestibulaires intenses et inhabituelles. Nous n'avons pas observé l’habituation vestibulaire attendue lors d’explorations fonctionnelles vestibulaires (RAIG et échelon de vitesse) en comparaison avec des sujets témoins, en revanche les pilotes étaient moins sensibles au mal des transports. Nous suggérons que les pilotes ne développent pas d'habituation vestibulaire comme attendu car ils ont besoin des réponses vestibulaires préservées et non altérées pour maintenir une performance optimum lors des activités de voltige aérienne.Nous concluons que pour générer des réponses en lien avec l’orientation, le système nerveux central intègre les signaux vestibulaires et non-vestibulaires et est sujet à un certain niveau de plasticité en conditions sensorielles altérées. Ce traitement multisensoriel est régulé individuellement, avec un poids variable des informations vestibulaires, en fonction de l'état sensoriel et des exigences liées à l’activitéThe aim of this thesis was to specify the role of the vestibular system in the orientation-related homeostasis. We evaluated vestibular responses to changes in orientation in space (1) in normal population to reveal in what proportion different sensory systems are implicated in the generation of the cardio-vascular and respiratory responses, and (2) in populations with altered vestibular afference: bilateral vestibular loss patients and aerobatic pilots.The results indicated that the vestibular system cooperates with trunk graviceptors to evoke respiratory response to changes in orientation during Off-Vertical Axis Rotation protocol (OVAR). The contribution of each sensory source was found to vary between individuals. Another study tested the hypothesis that the vestibular modulation of cardio-vascular parameters can be influenced by visual input during OVAR. Preliminary results from this study have demonstrated that the OVAR stimulation has an effect on the mean cardio-vascular parameters. The modulatory effect of OVAR on the arterial pressure has also been shown. The phases of modulation were varying between individuals which can indicate the neural nature of the observed modulation. The effect of visual stimulation on modulation has been detected, however further analysis is required. In another study, subjects presenting bilateral vestibular loss were shown to have the same cardio-vascular response to changes in the position of the head during Head-Down-Neck-Flexion protocol (HDNF) as normals. This reconstruction of the vestibulo-sympathetic reflex in human seems to originate from the sensory sources other than labyrinthine. Finally, we studied aerobatic pilots as humans experiencing intense and unusual vestibular stimulations. We have not revealed the expected vestibular habituation in the study using the OVAR and EVAR (Earth-Vertical Axis Rotation) stimulations, but were significantly less susceptible to motion sickness. We suggest that the pilots do not develop habituation, as they require unsuppressed responses for a better performance.We conclude that to generate the orientation-related responses, the Central Nervous System integrates the vestibular and non-vestibular signals and is subject to plastic changes in altered sensory conditions, if the response needs to be changed or restored. This multisensory processing is individually tuned, with the variable portion of vestibular impact in this processing, depending on activities, sensory state and the requirements to the response
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Chan, Lai-yung, and 陳麗蓉. "Early blockade of glutamate receptors within the vestibular nucleus deters the maturation of thalamic neurons in the system for detectionof linear acceleration." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B44658825.
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Gourgeon, Aurélie. "Régionalisation fonctionnelle du cortex cérébelleux postérieur chez le rat." Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS568.
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La représentation et la position du corps dans l'espace ainsi que la stabilisation du regard et de la posture dépendent fortement des mouvements de la tête. Pour ce faire, le système vestibulaire utilise deux types de capteurs inertiels : les canaux semi-circulaires pour la détection de la rotation de la tête et les organes à otolithes sensibles à sa translation. L’intégration de cette information inertielle s’effectue en partie dans complexe nodulo-uvulaire (CNU) et des enregistrements électrophysiologiques de cellules de Purkinje (CP) dans sa partie médiane, ont montré une intégration plus complexe de l’information vestibulaire que celle estimée jusque-là. Toutefois, l'organisation anatomique, moléculaire et cellulaire du CNU n’a, à ce jour, pas été considérée dans l’interprétation de la dynamique des cellules de Purkinje du CNU. Afin d’appréhender cette régionalisation anatomo-fonctionnelle, des enregistrements électrophysiologiques dans sa partie latérale ont été réalisés au cours de mouvements naturels et spontanés chez le rat et une ré-analyse des données médianes a été effectuée. Les résultats présentés dans cette thèse corroborent ceux publiés précédemment mais révèlent également une organisation inter-lobulaire et médio-latérale de l’activité des CP, montrant une répartition inégale des sensibilités inertielles. Par ailleurs, l’existence d’une nouvelle classe de cellules anticipant le mouvement a été révélée et constitue un argument supplémentaire à l’intégration d’un signal de « copie efférente » au sein du CNUThe representation and position of the body in space as well as the stabilization of gaze and posture heavily depend of head movements. Thus, the vestibular system uses two types of inertial sensors: the semi-circular canals for the detection of rotations of the head and otolith organs sensitive to its translation. The integration of this inertial information is partly done in the nodulo-uvular complex (CNU) and electrophysiological recordings of Purkinje cells (CP) in its median part, have shown a more complex integration of vestibular information than estimated until there. However, the anatomical, molecular and cellular organization of the CNU has so far not been considered in the interpretation of the CNU Purkinje cell dynamics. In order to apprehend this anatomo-functional regionalization, electrophysiological recordings in its lateral part were performed during natural and spontaneous movements in the rat and a re-analysis of the median data was done. The results presented in this thesis corroborate those previously published but also reveal an inter-lobular and medio-lateral organization of CP activity, showing an unequal distribution of inertial sensitivities. In addition, the existence of a new class of cells anticipating movement has been revealed and constitutes an additional argument to the integration of an "efferent copy" signal within the CNU
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Riddell, Clinton D. "Functional Morphology of the Vestibular End Organs in the Red-eared Slider Turtle, Trachemys scripta elegans." Ohio University Honors Tutorial College / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ouhonors1400600303.
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Hitier, Martin. "Relation du système vestibulaire avec l'hippocampe." Thesis, Normandie, 2017. http://www.theses.fr/2017NORMC426.
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Le système vestibulaire est le seul sens ne possédant pas un cortex primaire mais plusieurs zones corticales rassemblées sous le terme « cortex vestibulaire ». Le rôle et le fonctionnement du cortex vestibulaire restent peu connus à l’état physiologique, et encore moins chez des personnes souffrant de pathologies vestibulaires ou de l’intégration multisensorielle. Parmi ces régions, l’hippocampe joue un rôle fondamental dans la cognition d’origine vestibulaire et en particulier dans l’orientation spatiale et la formation de carte cognitive. Le but de ce travail était d’étudier la répartition des influx vestibulaires au sein de l’hippocampe, chez le rat qui représente l’espèce où les connaissances sur l’hippocampe sont les plus développées. Pour cela nous avons mis au point une méthode de lésion labyrinthique chirurgicale et une méthode de stimulation électrique sélective de chaque senseur vestibulaire (3 ampoules canalaires, les macules utriculaires et sacculaires). Cette méthode a ensuite été appliquée pour étudier le reflex vestibulo-oculaire spécifique de chaque senseur du rat. Ce reflex vestibulo-oculaire a ensuite était utilisée comme témoin d’une stimulation efficace et sélective de chaque senseur vestibulaire. Nous avons enfin étudié la projection des influx vestibulaires au niveau de l’hippocampe par analyse immunohistochimique de la protéine cFOS, considéré comme un marqueur de l’activité neuronale. Les résultats retrouvent une prédominance de cFOS au niveau de l’hippocampe dorsal, dans la région CA2-CA3. Ces résultats sont cohérents avec l’implication de l’hippocampe dorsal dans la cognition et le rôle de CA3 dans l’encodage de nouvelles informations spatiales, dans la mémoire à court terme et dans la représentation spatiale géométrique de l’environnementThe vestibular system is the only sense that lake a primary cortex but project to several cortical areas known as the "vestibular cortex". The roles and functioning of the vestibular cortex remain poorly known, neither in the physiological state, nor in pathologies involving the vestibular system. Among these cortices, the hippocampus plays a fundamental role in vestibular cognition and in particular in spatial orientation and cognitive map formation. The purpose of this work was to study the distribution of vestibular inputs within the rat’s hippocampus, which represents the species where hippocampus is best known. For this purpose we have developed a method of surgical labyrinthectomy and a method of selective electrical stimulation of each vestibular sensor (3 canals ampullae, utricular and saccular maculae). This method was then applied to study the vestibulo-ocular reflex specific of each sensor in the rat. This vestibulo-ocular reflex was further used during electrical stimulation of each sensor to control the effectiveness and selectiveness of the stimulation. Finally, we studied the vestibular imputs in the hippocampus by immunohistochemical analysis of the cFOS protein, which is considered as a marker of neuronal activity. The results show a predominance of cFOS labelling in the dorsal hippocampus, in the CA2-CA3 region. These results are consistent with the role of the dorsal hippocampus in cognition and the role of CA3 encoding of new spatial information within short-term memory and in processing the geometry of the environment