Abstract
It is apparent that visual information is used in maintaining stable posture in a stationary world. Considerable previous research has indicated that significant perturbations of posture can be induced with a shift in the entire visual scene. When standing or walking on moving platforms, it is assumed that posture and ambulatory ability are controlled more by vestibulo-spinal reflexes, but the role of visual reference has not been extensively studied. In the present study, we measured force plate recordings while subjects stood on a moving platform and derived the frequencies of motion-induced interruptions (MIIs) under two conditions. In the first condition a view of the stationary world within which the motion occurred was provided. In the second it was not. Subjects were tested on a motion platform driven by simulated ship-motion profile. In condition 1, subjects were allowed to see the walls and ceiling of the stationary test cubicle that housed the motion platform. In condition 2, curtains attached to the motion platform precluded this view. Significantly more MIIs (defined by differences in force plate recordings for the left and right feet) were found under the condition involving curtains. These results suggest that the visual input to postural stability in motion environments is more important than previously assumed. This suggests that manipulations (e.g. artificial horizons) that provide stable visual representations of the static environment within which the motion occurs may provide important health and safety measures for individuals working in enclosed environments on modern vehicular conveyances.