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 développement. / Earth’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.

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’environnement. / The 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.

Walden University College of Social and Behavioral Sciences This is to certify that the doctoral dissertation by Octavious Bishop has been found to be complete and satisfactory in all respects, and that any and all revisions required by the review committee have been made. Review Committee Dr. Thomas Edman, Committee Chairperson, Psychology Faculty Dr. Ricardo Thomas, Committee Member, Psychology Faculty Dr. Joanna Bissell-Havran, University Reviewer, Psychology Faculty Chief Academic Officer Eric Riedel, Ph.D. Quantifying the Spectrum of Depression by Octavious Bishop MA, University of Texas at Austin, 2008 BS, University of Texas at Austin, 2001 Dissertation Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy Psychology Walden University May 2018 Depression is a medically serious and widespread mood disorder that is difficult to diagnose in an objective manner. Dopamine irregularities have been strongly implicated in depression studies, and drug therapy based on dopamine is in wide use. However, the same neurological abnormalities associated with depression also affect other neural systems, including the vestibular system, in which involuntary muscle movements involved with the contralateral acoustic reflex are located. Using nigrostriatal pathways that transmit dopamine as a framework, this study investigated the biological and physiological links between depression and acoustic reflexes, and their potential usefulness for objectively assessing depression. Records of 52 randomly-selected patients who presented symptoms of depression were assessed to determine the relationship between depression and the contralateral acoustic reflex. The patients were both male and female, ranging in age from 23 to 84. Acoustic reflex threshold testing was assessed through ranges of frequencies using a tympanogram. The resulting individual average scores for the right ear and the left ear were then statistically tested against the medically accepted normal score using one-sample t tests. Evidence indicated that acoustic reflex abnormality may be concomitant with depression. These findings offer promising possibilities to researchers looking to develop a functional quantifiable assessment of patients who present with symptoms of depression. Addressing the wide variance of symptoms in patients may help mental health professionals determine which antidepressants to prescribe or if a patient is ready for a therapeutic process.

Self-motion perception is based on the integration of visual (optic flow) and vestibular (inertial) sensory information. Previous research has shown that the relative contribution of visual and vestibular cues can change in real time based on the reliability of that information. The present study assessed whether initial velocity and acceleration magnitude influence the relative contribution of these cues to the detection of self-acceleration. Participants performed a simple response time task with visual and vestibular self-acceleration cues as targets. Visual optic flow was presented at three possible initial velocities of 3, 9, or 15 m/s, and accelerated to result in three possible final velocities of 21, 27, or 33 m/s. Corresponding vestibular cues were presented at magnitudes between 0.01 and 0.04 g. The self-acceleration cues were presented at three possible stimulus onset asynchronies (SOAs): visual-first (by 100 ms), in-sync, and vestibular-first (by 100 ms). We found that presenting the cues in-sync resulted in the fastest responses across all velocities and acceleration magnitudes. Interestingly, presenting the visual cue first resulted in a relative advantage over vestibular-first at the slowest initial velocity of 3 m/s, and vice versa for the fastest initial velocity of 15 m/s. The fastest overall responses for visual-first and in-sync were observed at 9 m/s. The present results support the hypothesis that velocity of optic flow can alter the relative contribution of visual and vestibular cues to the detection of self-acceleration. / Thesis / Master of Science (MSc) / This thesis contributes valuable insight into the emerging literature on how visual and vestibular cues are integrated to result in reliable self-motion perception. Specifically, this thesis provides evidence that velocity of optic flow plays an important role in mediating the relative weighting of visual and vestibular cues during acceleration perception.

The quality of sensory information which is necessary for balance and postural stability is changing throughout aging. It is closely related to increasing cases of injury caused by fall of elderly people. The aim of the diploma thesis is to explain the effect of age to the postural stability especially during varied cervical spine positions. The theoretical part of the thesis deals with a control of balance, role of vision, vestibular and somatosensory system, influence of static and dynamic movements of cervical spine to postural control. Within the experimental part we carried out a posturographic examination of standing stability in two groups of healthy people varying age. The destabilization effect was objectify by measurement of the average velocity of center of pressure during upright head position, extension of cervical spine and theirs dynamic movements in sagittal plane. The extension of cervical spine increases difficulty of performance certain posturographic tests and it is used in unrevealed compensated deficits of stability. This unusual position causes falls in elder people. Destabilization effect is expected within increasing speed of the sagittal movement of the cervical spine during examination of dynamic locomotion. Control of stability and head orientation might be used for...

vi Abstract Title: Evaluation of postural stability among deaf adults Objectives: The purpose of this diploma thesis was to compare the postural stability between the deaf and the normal hearing adults, and to find out if the statistically significant difference in measured parameters does exist. Methods: 102 subjects at the age of 20-45 years participated in this study. The experimental group consisted of 35 deaf adult subjects with congenital or early childhood deafness. The control group has been made by 67 normal hearing adult subjects. The postural stability was objectively evaluated by Footscan, the pressure measuring plate. Nine tests were passed, duration of each test was 30 seconds. The total travelled way (TTW) expressing the total path the centre of acting pressure travelled during the test and the Romberg ratio, which is the ratio of TTW values under the condition of closed and open eyes, were selected as indicators of postural stability. T-test was used to assess the statistical significance of the differences between the group of deaf adults and normal hearing group. To estimate the influence of individual characteristics of the subjects (evaluating the data from the questionnaires) to their postural stability, the ordinary least squares estimator was used. Results: The experimental group was...

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Some 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.

Le système vestibulaire joue un rôle important pour plusieurs fonctions, notamment, la perception de mouvement et le maintien de l’équilibre par l’entremise du contrôle postural. Or, une dégradation de la fonction de ce système peut avoir un impact sur le contrôle postural et ainsi augmenter le risque de chutes. Au courant des dernières années, la stimulation vestibulaire galvanique noisy (nGVS) a été démontrée comme étant efficace pour stimuler le système vestibulaire et améliorer le contrôle postural. Toutefois, les données de la nGVS sont fragmentaires et les paramètres optimaux de stimulation n’ont pas été établis. L’objectif général de la thèse était d’examiner l’effet de la nGVS sur le contrôle postural. Plus précisément, cette thèse visait à déterminer la méthodologie optimale de la nGVS et l’influence de la nGVS sur le contrôle postural d’une population présentant une dégradation de la fonction vestibulaire, soit des personnes âgées. La première étude avait pour objectif d’examiner l’effet post-stimulation de la nGVS sur le contrôle postural comparativement à une stimulation placebo. Ainsi, 14 adultes ont reçu une stimulation nGVS alors que 14 autres adultes ont reçu une stimulation placebo (sham). Le contrôle postural a été examiné avant la stimulation, immédiatement après la fin de la stimulation et 1 heure post-stimulation. Les résultats ont démontré une amélioration posturale similaire chez le groupe nGVS et le groupe sham, suggérant donc l’absence d’effet de la nGVS et ainsi un biais expérimental. De ce fait, cette étude a souligné l’importance d’un groupe contrôle lors de l’étude des effets de la nGVS sur le contrôle postural. La seconde étude visait à examiner l’effet de la densité du courant de la nGVS sur le contrôle postural en manipulant la taille des électrodes de stimulation. 36 adultes ont été séparés en 2 groupes expérimentaux, recevant la nGVS, et 1 groupe contrôle, recevant une stimulation placebo. Les groupes expérimentaux recevaient la nGVS soit avec des électrodes 35 cm2 ou 3 cm2. Ainsi, une amélioration posturale significative a été induite par la nGVS appliquée avec les électrodes de 3 cm2, soit celles avec une densité de courant plus élevée, comparativement à la nGVS avec électrodes de 35 cm2 et la stimulation placebo. La troisième étude visait à examiner l’effet de la nGVS sur le contrôle postural de personnes âgées avec et sans atteinte vestibulaire. De plus, cette étude explorait également l’effet post-stimulation de la nGVS chez les personnes âgées en comparaison à une stimulation placebo. Pour ce faire, 24 personnes âgées ont reçu la nGVS, la moitié avait une atteinte vestibulaire et l’autre moitié avait une fonction vestibulaire normale, et 12 personnes âgées ont reçu une stimulation placebo. Les données ont révélé une amélioration significative du contrôle postural induite par la nGVS comparativement à la stimulation placebo. De plus, une plus grande amélioration posturale a été observée chez les personnes âgées avec atteinte vestibulaire que les sujets âgés avec fonction vestibulaire normale après l’arrêt de la stimulation. Les résultats ont également démontré que l’amélioration posturale induite par la nGVS était maintenue après l’arrêt de la stimulation. Globalement, ces études soulignent des considérations méthodologiques de la nGVS, précisément, l’importance d’une stimulation placebo et de la densité du courant. De plus, les résultats suggèrent également un effet bénéfique de la nGVS sur le contrôle postural de personnes âgées, et celles présentant une atteinte vestibulaire en bénéficieraient davantage. Toutefois, des études futures sont requises pour déterminer les effets à long terme de la nGVS et les applications cliniques. / The vestibular system plays an important role for self-motion perception and balance through postural control. Therefore, a vestibular impairment can notably lead to a decrease of postural control and a higher risk of falls. Recently, noisy galvanic vestibular stimulation has been shown to stimulate the vestibular system and thereby improves postural control. However, until now, the optimal methodology for nGVS has not been determined, and the influence of the vestibular function on the effect of nGVS on postural has not been studied. Therefore, the main objective of the thesis was to examine the effect of nGVS on postural control. More precisely, this thesis aimed at determining the optimal methodology to apply with nGVS and to examine the effect of nGVS in a population with a decreased vestibular function, namely older adults. The first study aimed at investigating the sustained effect of nGVS on postural control compared to a sham stimulation. 28 adults were recruited and they either received nGVS or a sham stimulation. Postural control was assessed before stimulation, immediately after stimulation and 1 hour post-stimulation. Results showed a similar improvement of postural control for nGVS and sham, therefore suggesting an experimental bias. This study underlined the importance of a sham stimulation in the exploration of the sustained effect of nGVS on postural stability. The second study aimed at examining the effect of nGVS current density on postural control. To manipulate current density, two different sizes of electrodes were used, therefore 12 adults received nGVS with 35 cm2 electrodes while 12 others received nGVS with 3 cm2 electrodes. The nGVS groups were compared to 12 adults receiving a sham stimulation. The results demonstrated that only nGVS applied with 3 cm2 induced a significant improvement of postural compared to nGVS applied with 35 cm2 and sham stimulation. Therefore, it suggested that higher current density is needed to improve vestibular function. The third study aimed at determining the effect of nGVS on postural control in older adults with and without vestibular impairment. Furthermore, a second objective was to examine the post-stimulation effect of nGVS in older adults compared to a sham stimulation. 36 older adults were recruited, and 24 received nGVS while 12 received a sham stimulation. The nGVS group was composed of 12 older adults with vestibular impairment and 12 with a normal vestibular function. The results revealed that nGVS significantly improved postural control of older adults compared to a sham stimulation. The improvement induced by nGVS was significantly greater in older adults with vestibular impairment compared to older adults with normal vestibular function after the end of stimulation. Furthermore, the effect of nGVS on postural control was sustained after the end of the stimulation period. In summary, these studies underlined important methodological parameters of nGVS and results showed that nGVS could be a promising approach to use with populations with a decreased vestibular function, such as older adults. However, further studies are needed to examine the extent of the sustained effect of nGVS on postural control and to evaluate clinical applications.

No description available.

No description available.