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Laura F Fox, Frank H Durgin; More recalibration of the perception of linear self-motion. Journal of Vision 2003;3(9):557. doi: 10.1167/3.9.557.
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© ARVO (1962-2015); The Authors (2016-present)
It has been demonstrated, using a treadmill, that adaptation to a mismatch between locomotor activity and visual feedback (optic flow) produces an aftereffect on the task of walking, without vision, to a previewed target (Rieser et al., JEP:HPP, 1995). We (Durgin, Fox, et al., Psychonomics, 2002) have recently demonstrated that a more powerful version of this aftereffect can be obtained from normal walking in a wide-area virtual reality (VR) with altered visual gain (relative optic flow rate). We attribute the greater effect to concomitant recalibration of vestibular signals. There were no changes in perceived distance, as assessed verbally. Hypothesizing that the aftereffect therefore entailed a recalibration of locomotor estimates of the rate of self-motion, we investigated whether subjects would also show changes in their drift rate when running in place without visual feedback (see Anstis, EBR, 1995; Durgin & Pelah, EBR, 1999), after adapting to the same VR experience. Subjects' drift (rate of inadvertent forward advance while attempting to run in place with eyes closed) was assessed before and after adaptation. Adaptation consisted of exposing subjects to 5 minutes walking at a normal pace (∼4 kph) back and forth in a hallway in which the visual gain (in VR provided via an HMD) was either too high or too low by a factor of two. Subjects who were adapted to low visual gain demonstrated increased posttest drift, and those adapted to high visual gain tended to show reduced posttest drift. Asymmetries in the effects of high and low gain were quantitatively similar to those found for target-walking tasks in our previous study. The results provide a unique demonstration of altered drift rate modulated by the relative rate of optic flow during normal walking. They also strongly support the conjecture that the two aftereffects (altered drift rate and altered locomotor gain in walking without vision) have a common source (Durgin, Pelah, et al., ARVO, 1998).
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