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Melissa Parade, Brett R. Fajen; Does optic flow calibrate foot placement when stepping on a target?. Journal of Vision 2012;12(9):191. doi: 10.1167/12.9.191.
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Changes that affect a person’s body or the environment may produce differences between intended and actual movements. When such changes take place, visuo-motor adaptation allows people to compensate for such errors. Previous research has shown that optic flow is sufficient to drive adaptation to changes in the speed and direction of locomotion, and that adaptation transfers to several functionally similar tasks. In this study, we ask whether optic flow is also sufficient to calibrate precise foot placement when stepping on targets on the ground. The experiment was conducted in an immersive virtual environment (VE) viewed through a head-mounted display. The position and orientation of the head and the feet were tracked by motion capture equipment. Subjects began each trial by standing at a designated home location. When they pressed a button on a handheld remote mouse, a small, rectangular foot target appeared within one step-length of the home location. Subjects were instructed to step on the target and continue walking to a goal post several meters ahead. The entire VE disappeared as soon as subjects began moving such that visual feedback was eliminated while stepping on the target. The VE then reappeared shortly after subjects completed their first step such that optic flow was available while subjects walked to the goal post. Subjects completed three blocks of trials -- an adaptation block during which we manipulated the speed with which subjects moved through the VE (visual gain), and a pre- and post-test during which visual gain was normal. Analyses focused on the effects of the visual gain manipulation on the accuracy of stepping to the ground target as well as the rate and magnitude of recalibration.
Meeting abstract presented at VSS 2012
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