Postural Stability During Treadmill Locomotion as a Function of the Visual Polarity and Rotation of a Three-Dimensional Virtual Environment

Visual inputs provide us with important cues for orientation and self-movement perception during locomotion. The purpose of the present study was to better understand and quantify the effects of visual scene variables: visual polarity and visual scene rotation on postural stability during treadmill locomotion. During 60 s trials, subjects walked at 4.0 km/h while viewing a monoscopic, passive-immersive, 3D virtual room environment that contained either polarized or nonpolarized content and was back-projected onto a screen 1.5 m in front of them, one at a time. Scenes remained static for the first 30 s, then rotated about the roll, pitch, or yaw axis of the room at a constant rate of 30/s for the remaining 30 s. Each subject saw each combination of visual polarity (polarized, nonpolarized) and scene rotation direction (roll, pitch, yaw) for three separate trials. There was a main effect of visual polarity on variability in torso linear X (foreaft) position and torso roll and pitch angular orientations with polarized scenes causing more variability than nonpolarized scenes. For the polarized scenes only, variability in torso roll, pitch, and yaw angular orientations was increased for corresponding scene rotation directions, respectively. In general, rotating visual scenes caused increased variability in torso motion compared to static scenes. Visual polarity is an important consideration when designing virtual environment motion simulations.

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