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Patterning Principles in Vertebrate Sensory Systems
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- Author / Creator
- Long, Rebecca M.
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Patterns are predictable, ubiquitous, and functional. In something as complex and vast as the nervous system, patterns play an important role in maintaining order through logical organization. Sensory systems are one such example where neuronal organization show common patterns across modalities. From the distributions of different sensory receptors in their terminal organs, to the final central organization in cross-modality integrative regions, consistencies appear across both senses and species. This thesis will describe different aspects of patterning techniques employed at all levels of sensory processing, in three animal models covering a wide range of vertebrate phylogeny.
The first project focuses on one proposed theory of how patterns form, using the adult mammalian peripheral nervous system (PNS) as a model. The adult mammalian PNS, which is at constant risk of injury and disruption, must have a guidance mechanism to help re-pattern sensory nerve fibre terminations following an injury in the adult animal. We investigate the clustered protocadherins and their role in the control of outgrowth and spacing of somatosensory terminals in the skin and show how protocadherins may exert an inhibitive effect on the outgrowth of regenerating axons. This project also discusses how they are likely employed in organizing neurons of the same subtype following a peripheral nerve injury, which is necessary to maintain proper sensory feature separation.
The second project investigates the organization of primary sensory projections once they enter the central nervous system. The distribution of primary projection terminals of the vestibular system in snakes, a relatively unique and understudied clade of reptiles, show similarities in the distribution patterns with other reptilian and non-reptilian organisms. Utilizing a novel tracing technique in an ex vivo prep, we show that the patterns exhibited by primary terminations are divided by the sensory feature detected, and that this pattern seems to be consistent with other studied vertebrates.
Finally, the third project focuses on the function of a pattern. Sensory systems exhibit modular organization, and when integrating across modalities, this modular organization remains conserved. As individual features of sensory stimuli are segregated at the point of transduction, as well at the point of primary cortex, this separation is maintained all the way up until higher cortex where they then can be integrated with other modalities. Using the vestibulocerebellum of the pigeon as a model, we examine these alternating modular zones. We show that each zone has distinct electrophysiology and speculate how they could integrate the visuo-vestibular input to participate in the modulation of direction specific vestibulo-ocular reflexes.
By understanding different aspects of patterning in the sensory nervous systems, and how the architecture is common across vertebrates, we can make inferences into how they work based on similarities in other systems within the brain. -
- Graduation date
- Fall 2020
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- Type of Item
- Thesis
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- Degree
- Doctor of Philosophy
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- License
- Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.