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Michiteru Kitazaki, Taku Hashimoto; Effects of perspective jitter on vection and visual control of posture are dissociated. Journal of Vision 2006;6(6):149. doi: 10.1167/6.6.149.
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Vection is visually-induced self-motion perception. Palmisano and his colleagues (2000, 2003) reported the adding global-perspective jitter on expanding optical flow improved vection. We aimed to test if different types of jitter simulating viewpoint-change and/or eye-movement, and if the jitter enhanced both vection and postural sway. We simulated a linear forward/backward motion of the viewpoint in a 3-D cloud of dots (2730dots visible) and projected on a large screen (91x75deg). Four types of optical flow were used. (1) No-jitter condition was just a straight motion of viewpoint without jitter. (2) Viewpoint-jitter condition was a simulation of vertical oscillation (0.96Hz, amplitude 2.29deg) of viewpoint (eye position). (3) Eye-movement-jitter condition was a simulation of vertically oscillating eye-movement. (4) Line-of-sight-jitter condition was a simulation of vertical oscillation of line-of-sight (combination of (2) and (3)). Randomized 8 conditions (2 motion directions x 4 jitter conditions) were presented 10 times. Vection latency and postural sway were measured for 10 naive subjects. We found improvement of vection by any type of jitter (latency 1>2=3=4). Thus, the effective jitter is not specific to type of viewpoint/eye-movement, but generic. The jitter effect was more explicit in forward self-motion than backward self-motion. Observers inclined in the opposite direction of simulated self-motion, however, its amplitude was not affected by jitter. Since the jitter effect was specific to vection, it is suggested the processes for vection and visual control of posture are dissociated before the jitter modulates self-motion perception.
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