Several studies have examined the influence of optic flow presented in the central and peripheral fields of view on postural sway, but they have yielded diverging results. Early reports suggested that movement in the periphery was associated with increased sway. Later studies have argued that central movement is equally important. The primary objective of this set of experiments was to further investigate the influence of central and peripheral optic flow on postural equilibrium. The postural sway of 20 healthy subjects (ages 21-30 years) was measured while they viewed moving visual stimuli in a computer-generated immersive environment encompassing their entire horizontal field-of-view (FOV). Two main studies were conducted. In the first, optic flow was presented at different FOVs, but the motion contained only one frequency component during each trial. In the second, the central and peripheral regions of the visual stimulus moved simultaneously but at different frequencies.
In the first experiment, the location of the optic flow stimulus significantly affected the number and size of significant postural responses. There were twice as many significant postural responses to the peripheral optic flow condition compared to the central optic flow. In addition, the magnitude of the response to the peripheral optic flow was 6.5 times greater than the response to the central flow. The number and magnitude of significant responses were also greater for higher-frequency stimuli, after accounting for quiet-stance sway components.
In the second experiment, there were 3.5 times as many significant postural responses to the peripheral optic flow stimulus as there were to the central optic flow. Likewise, the amount of sway was greater in response to the peripheral stimulus.
The results of both experiments suggest that the postural system is more sensitive to anterior-posterior optic flow in the peripheral FOV, regardless of stimulus frequency. These findings have implications for the use of virtual environments, showing that head-mounted displays with a limited central FOV do not provide the visual information most important for postural control. Furthermore, the results suggest that rehabilitation therapists should incorporate peripheral movement cues in treatment to enhance balance retraining.
| Identifer | oai:union.ndltd.org:PITT/oai:PITTETD:etd-11202003-123235 |
| Date | 02 February 2004 |
| Creators | Jasko, Jeff G |
| Contributors | Patrick Loughlin, Mark Redfern, Patrick Sparto |
| 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-11202003-123235/ |
| 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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