Effects of a fixed point on postural readjustments caused by a moving visual scene.

This study examined how postural readjustments caused by a moving scene can be affected by placing a fixed point (FP) onto the moving scene. Thirty-two healthy subjects participated in this study. Each subject maintained Romberg's position on a platform while vertical optokinetic stimulation (VOKS) was presented. A random dot pattern moving in a downward direction was projected on a large hemispherical screen placed in front of the subject. The magnitude of vection and forward displacement from the center of foot pressure (CFP) caused by VOKS were compared under two conditions: with and without FP. With FP, the magnitude of vection increased towards slow VOKS velocity, while forward displacement of CFP decreased significantly. These results indicate that an FP placed in a moving pattern may contribute to stabilizing postural orientations.