Changes in posture are detected by the central nervous system through a number of sensory afferents. The vestibular labyrinths are one such sensor that discern rotational and accelerative movements of the head. The vestibular nuclei, the primary processor of labyrinthine input, coordinates several system outputs to maintain stable balance, visual gaze, and autonomic control in response to changes in posture. Following destruction of bilateral labyrinths, organisms are unable to effectively interact with their environment. Over time, these animals adapt due to some currently undefined process. It is our hypothesis that the observed behavioral recovery is due to a process that occurs within the vestibular nuclei. The nuclei regain their functional ability to sense changes in posture through substitution of sensory inputs from remaining non-labyrinthine afferents. Ascending spinovestibular afferents are ideal sources of plasticity, as they are ideally situated to convey this postural information.
Recordings were made from the vestibular nuclei of decerebrate cats that had undergone a combined bilateral labyrinthectomy and vestibular neurectomy 49103 days previously and allowed to recover. Responses of neurons were recorded to tilts in multiple vertical planes at frequencies ranging from 0.05 to 1 Hz and amplitudes up to 15°. The firing of 27% of the neurons was modulated by tilt. These findings show that activation of vestibular nucleus neurons during vertical rotations is not exclusively the result of labyrinthine inputs, and suggest that limb and trunk inputs may play an important role in graviception and modulating vestibular-elicited reflexes.
In the second portion of this work, we examined the spinal contributions to the vestibular nuclei in both labyrinthectomized and normal animals. The large majority (72%) of vestibular nucleus neurons in labyrinth-intact animals whose firing was modulated by vertical rotations responded to electrical stimulation of limb and/or visceral nerves; the activity of even more vestibular nucleus neurons (93%) was affected by limb or visceral nerve stimulation in chronically labyrinthectomized preparations. These data suggest that nonlabyrinthine inputs elicited during movement will modulate the gain of responses elicited by the central vestibular system, and may provide for the recovery of spontaneous activity of vestibular nucleus neurons following peripheral vestibular lesions.
| Identifer | oai:union.ndltd.org:PITT/oai:PITTETD:etd-08192004-110017 |
| Date | 24 September 2004 |
| Creators | Jian, Brian Joobeen |
| Contributors | Dan Simons, Alan F Sved, Bob Schor, J. Patrick Card, Bill J Yates, Adrian Perachio |
| Publisher | University of Pittsburgh |
| Source Sets | University of Pittsburgh |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.library.pitt.edu/ETD/available/etd-08192004-110017/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Pittsburgh or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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