The outer spiral network and its innervation by the olivocochlear system
Thesis (Ph. D.)--Harvard-MIT Division of Health Sciences and Technology, 2008.
| Main Author: | |
|---|---|
| Other Authors: | |
| Format: | Thesis |
| Language: | eng |
| Published: |
Massachusetts Institute of Technology
2008
|
| Subjects: | |
| Online Access: | http://hdl.handle.net/1721.1/43871 |
| _version_ | 1811092577680621568 |
|---|---|
| author | Thiers, Fabio Albuquerque |
| author2 | Joseph B. Nadol, Jr. |
| author_facet | Joseph B. Nadol, Jr. Thiers, Fabio Albuquerque |
| author_sort | Thiers, Fabio Albuquerque |
| collection | MIT |
| description | Thesis (Ph. D.)--Harvard-MIT Division of Health Sciences and Technology, 2008. |
| first_indexed | 2024-09-23T15:20:25Z |
| format | Thesis |
| id | mit-1721.1/43871 |
| institution | Massachusetts Institute of Technology |
| language | eng |
| last_indexed | 2024-09-23T15:20:25Z |
| publishDate | 2008 |
| publisher | Massachusetts Institute of Technology |
| record_format | dspace |
| spelling | mit-1721.1/438712019-04-11T13:34:47Z The outer spiral network and its innervation by the olivocochlear system Thiers, Fabio Albuquerque Joseph B. Nadol, Jr. Harvard University--MIT Division of Health Sciences and Technology. Harvard University--MIT Division of Health Sciences and Technology. Harvard University--MIT Division of Health Sciences and Technology. Thesis (Ph. D.)--Harvard-MIT Division of Health Sciences and Technology, 2008. Includes bibliographical references (leaves 125-135). Outer hair cells (OHCs) are key elements of the mammalian hearing system, which amplify sound-evoked signals transmitted into the inner ear. OHCs are innervated by peripheral projections of olivocochlear (OC) and type-II spiral ganglion neurons. Type-II neurons innervate up to 100 OHCs, but their function is unknown. It has been suggested that type-II neurons interconnect neighboring OHCs through reciprocal synapses, which are bi-directional (afferent and efferent) synaptic interactions (Nadol, 1981). Since reciprocal synapses on the OHCs have been shown to be prevalent only in aged primates, they were thought to be a pathological finding. In addition to their interactions with OHCs, type-II neurons are also innervated by OC neurons. Synapses between OC and type-II neurons (OC/type-II synapses) have been described (Smith and Rasmussen, 1963), but these interactions have not been characterized in detail. Serial and semi-serial section transmission electron microscopy were used to study the synaptic interactions of type-II neurons with OHCs and OC neurons in a young human and in adult cats. A high prevalence of nerve terminals with reciprocal synapses was observed in the young human and in adult cats. These reciprocal terminals were processes of type-IIs, and not of OC neurons. Reciprocal type-II terminals were found in all frequency regions studied in cats, but were most prevalent below 4,000Hz. All the type-II fibers traced to more than one OHC in an adult cat had reciprocal interactions with OHCs. Type-II fibers/terminals were heavily innervated by OC neurons, which preferentially targeted terminals with reciprocal synapses that were predominantly afferent in an adult cat. (cont.) The innervation patterns of type-IIs and OC neurons in the cat were similar to that found in comparable frequency regions of primates. Type-II neurons have reciprocal synaptic interactions with OHCs and form an "outer spiral network", which may functionally integrate the OHCs. The OC system may modulate this network through OC/type-II synapses. The outer spiral network and its innervation by the OC system seem to be relevant to OHC function, and further research is needed to determine their role in hearing. by Fabio Albuquerque Theirs. Ph.D. 2008-12-11T18:42:56Z 2008-12-11T18:42:56Z 2008 2008 Thesis http://hdl.handle.net/1721.1/43871 263428464 eng M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission. http://dspace.mit.edu/handle/1721.1/7582 135 leaves application/pdf Massachusetts Institute of Technology |
| spellingShingle | Harvard University--MIT Division of Health Sciences and Technology. Thiers, Fabio Albuquerque The outer spiral network and its innervation by the olivocochlear system |
| title | The outer spiral network and its innervation by the olivocochlear system |
| title_full | The outer spiral network and its innervation by the olivocochlear system |
| title_fullStr | The outer spiral network and its innervation by the olivocochlear system |
| title_full_unstemmed | The outer spiral network and its innervation by the olivocochlear system |
| title_short | The outer spiral network and its innervation by the olivocochlear system |
| title_sort | outer spiral network and its innervation by the olivocochlear system |
| topic | Harvard University--MIT Division of Health Sciences and Technology. |
| url | http://hdl.handle.net/1721.1/43871 |
| work_keys_str_mv | AT thiersfabioalbuquerque theouterspiralnetworkanditsinnervationbytheolivocochlearsystem AT thiersfabioalbuquerque outerspiralnetworkanditsinnervationbytheolivocochlearsystem |