It has been established that information from the visual, somatosensory, and vestibular systems contributes to balance, but how this information is integrated remains unclear. Sensory integration is a temporally dynamic process in which the sources for sensory information are dynamically regulated and change as environmental conditions change. Significant differences in this dynamic regulation have been found among healthy young and old subjects, as well as subjects with vestibular disease.
The present research was designed to examine the impact of aging and unilateral vestibular disease on balance as subjects responded to rapid changes in visual and somatosensory input. The postural sway of 25 healthy young controls, 24 healthy older controls, and 7 older subjects with unilateral vestibular hypofunction (UVH) was measured while visual and proprioceptive transitions were induced. To produce a sudden change in the visual environment, the amplitude of a sinusoidally moving visual scene was rapidly increased. Somatosensory information was altered through the use of a support platform that rotated in proportion to body sway, thereby reducing information from the somatosensory system.
The power of anterior-posterior head velocity was calculated for the 20 s surrounding each transition. This segment was then broken into 5 s periods in order to investigate adaptation, i.e. within-trial time-varying characteristics of postural sway. Habituation was studied by investigating the changes in postural sway over repeated trials. A mixed factor repeated measures ANOVA was conducted with the power of postural sway velocity (dB) as the dependent variable. The independent variables were trial repetition and the time period in relation to the stimulus transition. Subject type was the between-subjects factor.
Both healthy and vestibularly impaired older subjects were observed to sway more than healthy younger subjects during all experimental conditions. Following a decrease in reliable somatosensory input, all subjects showed an increase in postural sway power. This increase was greatest in older subjects with UVH. Though adaptation following the perturbation was seen in all subject groups, this process was slower in the patient group. Habituation was seen in most trial conditions, especially between the first and second presentations of a stimulus.
| Identifer | oai:union.ndltd.org:PITT/oai:PITTETD:etd-04052006-104840 |
| Date | 02 June 2006 |
| Creators | O'Connor, Kathryn Winchell |
| Contributors | Patrick Sparto, Mark Redfern, Patrick Loughlin |
| 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-04052006-104840/ |
| 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. |
Page generated in 0.0174 seconds