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Vivian Holten, Stella F. Donker, Maarten J. van der Smagt, Frans A.J. Verstraten; Caught off-balance by the motion aftereffect. Journal of Vision 2013;13(9):1332. doi: 10.1167/13.9.1332.
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© ARVO (1962-2015); The Authors (2016-present)
Visual stimuli simulating self-motion through the environment can induce potent postural adjustments in observers. This suggests a rather direct, stimulus driven, mechanism subserving these visuo-vestibular interactions. Here we examine whether visual-motion induced sway is the result of predominantly external stimulation, or whether it can be induced by an (illusory) internal representation of visual motion, as apparent in the motion-aftereffect (MAE) as well. We presented a random-pixel-array (RPA) (pixel size ~0.08 degrees, viewed through either a 8x8 degree or 87x56 degree aperture) translating at ~3 deg/s leftwards or rightwards during adaptation. A static version of the RPA, or a dynamic version, where each pixel was refreshed every 16.7 ms, were used as test pattern. Observers, standing on a force plate in a completely dark room in front of the projection screen, received an initial 40s adaptation, followed by 20s top-up adaptation epochs, that were interleaved by 14s test pattern epochs (either static or dynamic, presented in pseudo-random order). Each type of test pattern was presented 20 times per condition. Observers had to press a button to report when the MAE had dissipated (if <14s). MAE duration was longer for static than dynamic test patterns. Using the large aperture we observed more postural sway for a static than a dynamic test pattern, and the amount of sway appeared related to the strength (i.e. duration) of the illusory motion. For the small RPA, no difference in postural sway between the two test patterns was observed. The results demonstrate that illusory motion caused by a MAE can induce postural sway of which the amount depends on the test pattern and stimulus size. This suggests that visuo-vestibular interactions observed in visual-motion induced sway can at least be modulated by the conscious visual experience.
Meeting abstract presented at VSS 2013
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