The peripheral vestibular membranous ducts that detect angular motion are contained within bony semicircular canals of mammalian petrosals. I investigated morphology and function in the three membranous semicircular ducts through measurements on the bony semicircular canals of 31 skeletonized skulls from different genera. While the prevailing theory of semicircular canal researchers is that the locomotor agility of extant and extinct mammals can be understood by measuring the size of the three bony semicircular canal arcs, I propose that there are important and quantifiable features other than the adult size of radius of curvature of the semicircular canal arc (R) that influence angular movement detection in mammals and perhaps in their ancestors. Initially, I sought to verify that there was no significant asymmetry of R across the study specimens. However, there was significant asymmetry in canal pair angles between contralateral sets: ipsilateral canal pair angles differed by up to 14◦, and contralateral synergistic angle pairs differed by up to 18◦. Canal pair contralateral differences were lower for specimens of more agile taxa. In addition, the angle between the left and right lateral canals varied by up to 27◦ from parallelism, so the use of the lateral bony canal in one petrosal to represent the horizontal animal resting position could result in significant skull orientation errors. I utilized a program to quantify the effects of canal plane non-orthogonality and to calculate a maximum rotational sensitivity axis for a given taxon. My results concur with earlier research indicating that canal orientation significantly affects the location of maximum rotational sensitivity axes in the head, and should be considered in future quantitative research. Finally, I determined the volumes of the subarcuate fossa and the petrosal lobule in three Monodelphis domestica animals (76 days postnatal) by utilizing both cranial and tissue volumes in fresh specimens. The petrosal lobule fills 93-97% of the Monodelphis domestica fossa, a greater volume than the 50% estimated by previous researchers. These results highlight the difficulties of using histologic or preserved specimens to make quantitative determinations of brain tissue volumes, and reopen the question of whether the subarcuate fossa volume provides a record of the agility for an extinct taxon. / text

published_or_final_version / abstract / Physiology / Master / Master of Philosophy

Thesis (M. Phil.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

<p>Reconstructing locomotor patterns from fossils is crucial for understanding the origins of primates and important transitions in various primate clades. Recent studies suggest that the semicircular canals of the inner ear provide evidence about locomotion. The canals sense rotational head accelerations and drive reflexes essential for normal movement. Because bony aspects of canal morphology influence canal sensitivity, this system can be studied in osteologic specimens and fossils. Variation in canal morphology in living and, by inference, extinct primates has been attributed to interspecific differences in locomotor behavior. However, the manner in which movement selects for canal morphology is debated, alternative scenarios are plausible, and no relevant measurements are available documenting head movements in primates.</p><p>To refine proposed links between canal morphology and locomotor function, and to resolve conflicting functional interpretations, this study examines head rotations in lemurs and lorises exhibiting diverse locomotor behaviors. Three-dimensional kinematic analyses were used to characterize angular velocities of the head during locomotion. These data are used to test hypotheses concerning intraspecific, interspecific, and body-size dependent variation in head rotations. Cranial CT scans are used to model canal sensitivity to rotations in different directions. Observed patterns of head rotation are compared to predicted patterns of sensitivity to test hypotheses about the relationship between locomotor behavior and canal design.</p><p>Evaluation of existing locomotor inferences reveals that brain size exerts a significant effect on canal size and that the prevailing equations for predicting agility from body and canal size are highly inaccurate. Intraspecific comparisons between maps of observed angular velocity and predicted sensitivity allow identification of map types associated with different general locomotor modes and do not support existing hypotheses about the primary selective forces acting on canal morphology. The new data are used to formulate and test a novel "fast-accurate hypothesis" to explain why all vertebrates are more sensitive to rotations about some axes than others. The fast-accurate hypothesis stipulates that angular velocities presented about axes of mean sensitivity are most accurately interpreted by the brain, and that selection aligns axes of mean sensitivity with axes of habitually fast rotation because accurate perception of rapid rotations confers survival benefit. The fast-accurate hypothesis was used to predict which features of the canals should be correlated with high mean angular velocities of head movement. Novel equations that predict behavior from these newly identified canal morphologies were generated and found to outperform existing equations when tested on the original sample of 11 strepsirrhine species.</p> / Dissertation

<p>The semicircular canals of the vestibular system detect angular head rotations and play a fundamental role in guiding motor reflexes during locomotor behaviors. While extensive research has documented the relationship between the semicircular canal shape (i.e. radius of curvature and canal length) and locomotor behaviors, levels of intraspecific variation in primates are relatively unknown. Predictive models using these metrics to reconstruct locomotion in extinct animals are generally based on one individual per species. Furthermore, the influence of body size and to a lesser degree brain size heavily influences overall canal morphology.</p><p>This study documents intraspecific variation in the size, shape and orientation of the semicircular canals in relation to changes in function, brain size, and body size via analysis of high resolution CT scans of large samples of extant primate species. I test the hypothesis that the extent of intraspecific variation differs across a sample of primates, reflecting the intensity of selective pressure on canal shape in species that require agility during locomotion. I also examine whether spatial constraints resulting from the size of the skull (reflected by the size of the brain) affect canal radii of curvature and canal orthogonality more strongly than observed agility during locomotion. </p><p>To this end, data was gathered from high-resolution CT images of museum specimens. For the comparative analysis, 14-matched pairs of adult extant primate species were selected that contrast in agility and brain size in closely related genera. CT images of these specimens were used to measure functional measures of canal sensitivity (e.g., canal radii of curvature, orthogonality). This data was used to test hypotheses concerning intraspecific and interspecific variation in semicircular canal functional morphology. This data was then combined with a larger mammalian dataset culled from the literature, to further test hypotheses relating to body-size and brain size dependent variation in individual canal metrics. </p><p>Evaluation of levels of intraspecific variation support the hypothesis put forth by Billet et al. (2012), that selection on canal morphology is relaxed in animals with slow locomotor behaviors, who are observed to have higher levels of intraspecific variation. Analyses of interspecific variation provides tentative support for the use of canal orthogonality in reconstructive models, most especially in canal angles that seem least effected by other constraints—brain size, etc. However, locomotor signals are complex and brain/skull interactions can potentially produce misleading results when reconstructing locomotor behaviors. This work highlights the importance of critically assessing comparative groups used for inferring behaviors in both extinct and extant animals.</p> / Dissertation

Thesis. 1977. M.S.--Massachusetts Institute of Technology. Dept. of Aeronautics and Astronautics. / Microfiche copy available in Archives and Barker. / Bibliography: 142-145. / by Susan A. Riedel. / M.S.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1980. / Microfiche copy available in Archives and Barker. / Bibliography: leaves 193-197. / by Troy A. Crites. / M.S.

The semicircular canals detect head rotations and trigger compensatory movements that stabilize gaze and help maintain visual fixation. Mammals with large eyes and high visual acuity presumably require more precise gaze stabilization mechanisms because they experience degradation of spatial resolution at a lower threshold of uncompensated motion. Because semicircular canal radius of curvature is a primary determinant of canal sensitivity, species with large canal radii are expected to be capable of more precise gaze stabilization than species with small canal radii. Here the relationship between semicircular canal radius of curvature, eye size, and visual acuity is examined in a large sample of therian mammals. These results demonstrate that eye size and visual acuity both explain a significant proportion of the variance in mean canal radius of curvature after statistically controlling for the effects of body mass and phylogeny. These findings suggest that interspecific variation in semicircular canal radius of curvature is partly the result of selection for improved gaze stabilization in species with large eyes and acute vision. / text

Introduction: The dizziness is observed among 5 and 10% of the world population, affecting both genders. It can be of two sorts: rotatory (vertigo) or non-rotatory. The dizziness crises may injure the patients life, leading to the reduction of social coexistence and difficult the daily activities. The most common rotatory dizziness is the Benign Positional Paroxysmal Vertigo. The episodes are generally quick and triggered by the head movement, Furthermore, it may be accompanied by nausea, vomiting and fall. The diagnosis of Benign Positional Paroxysmal Vertigo is achieved through the Dix-Halpike maneuver, which shall verify the presence of nystagmus and/or giddiness. There are no reports of variation in conventional tests of patients with complaint of Benign Positional Paroxysmal Vertigo. It is observed only in vectonystagmography. The treatment of this type of dizziness is performed by canalith repositioning maneuvers. Objective: To verify the results found in the evaluations carried out by patients with Benign Positional Paroxysmal Vertigo, with emphasis on the results found in vectonystagmography and its relationship with affected semicircular canal. Material and Method: The study was performed in otology ambulatory of University Hospital of Santa Maria. The sample was composed of all patients who attended the ambulatory with complaints of. The patients have performed anamnesis, Dix-Halpike maneuver, vectonystagmography and Epley maneuver. They were divided in two groups: the control group, composed by patients with negative result in Dix-Halpike maneuver, and the study group, composed by patients with positive result in this maneuver. Results: There was prevalence of females among the patients and the average age was 57 years. The semicircular canal most affected was the anterior and the theory that prevailed was the ductolitiase. The average number of maneuvers necessaries to abolish the positioning nystagmus is 1.58 and there were 4 (6.9%) cases of recurrence. When analyzed the evidence of vectonystagmography, it was observed the presence of spontaneous nystagmus and a change in rotator testing. However, these variations are not related to the affected semicircular canal. It has occurred a predominance of normorreflexia in the caloric testing. Conclusion: The Epley maneuver is effective for patients with Benign Positional Paroxysmal Vertigo, even in cases in which they occur relapses. The variations found in vectonystagmography are not related to the affected semicircular canal. In fact, these variations are arising from the spontaneous and latent nystagmus presence. Consequently, it was not possible to verify other methods for the diagnosis of Benign Positional Paroxysmal Vertigo. / Introdução: A tontura é observada entre 5 e 10% da população mundial, atingindo ambos os gêneros. Pode ser de dois tipos: rotatória (vertigem) ou não rotatória. As crises de tontura podem prejudicar a vida do paciente, levando à redução do convívio social e dificultando as atividades de vida diária. O tipo de tontura rotatória mais comum é a Vertigem Posicional Paroxística Benigna. Os episódios geralmente são rápidos e desencadeados pelo movimento de cabeça, podendo ser acompanhado de náuseas, vômitos e queda. O diagnóstico de vertigem posicional paroxística benigna é realizado através da manobra de Dix-Halpike, que verifica a presença de nistagmo e/ou tontura. Não há relatos de alteração nos testes convencionais de pacientes com queixa de Vertigem Posicional Paroxística Benigna. Isto é verificado apenas na vectoeletronistagmografia. O tratamento desse tipo de vertigem é realizado pela manobra de reposição canalítica. Objetivo: verificar os resultados encontrados nas avaliações realizadas pelos pacientes com Vertigem Posicional Paroxística Benigna, com ênfase nos resultados encontrados na vectoeletronistagmografia e sua relação com o canal semicircular afetado. Material e Método: o estudo foi realizado no ambulatório de otologia do Hospital Universitário de Santa Maria. A amostra foi composta por todos os pacientes que compareceram ao ambulatório com queixa de vertigem posicional paroxística benigna. Os pacientes realizaram anamnese, manobra de Dix-Halpike, vectoeletronistagmografia e manobra de Epley. Estes foram divididos em dois grupos: grupo controle, composto pelos pacientes com resultado negativo na manobra de Dix-Halpike, e grupo estudo, composto pelos pacientes com resultado positivo nesta manobra. Resultados: Houve prevalência do sexo feminino entre os pacientes e a média de idade foi de 57 anos. O canal semicircular mais afetado foi posterior e a teoria que prevaleceu foi a ductolitíase. O número médio de manobras necessárias para abolir o nistagmo de posicionamento é 1,58 e houve 4 (6,9%) casos de recidiva. Quando analisada as provas da vectoeletronistagmografia, foi observada presença de nistagmo espontâneo e alteração na prova rotatória pendular decrescente. Entretanto, essas alterações não estão relacionadas com o canal semicircular afetado. Na prova calórica houve predomínio da normorreflexia. Conclusão: A manobra de Epley é eficaz para pacientes com vertigem posicional paroxística benigna, mesmo nos casos em que ocorrem recidivas. As alterações encontradas na vectoeletronistagmografia não estão relacionadas com o canal semicircular afetado. De fato, essas alterações são decorrentes da presença de nistagmo espontâneo e nistagmo latente. Consequentemente, não foi possível verificar outros métodos para o diagnóstico da vertigem posicional paroxística benigna.

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