Abstract
When you are on a still train and the train next to your train is moving, you would feel you are moving and you might lose your body balance. Thus, visual stimuli influence postural control and the perception of self-motion. Our previous research (Tsuruhara & Kaneko, 2004) showed that the center of subjects' body shifted along with the rotation of a large-stimulus of natural scene, and returned back with a bias remained after the stimulus stopped with a tilt. The perceived stimulus-tilt and self-tilt for the same stimulus, on the other hand, didn't change with time systematically. These results indicate that the bias of center of balance wouldn't cause the inaccurate stimulus- tilt or self-tilt perception, or vice versa.
Many studies have claimed that dorsal pathway would be mainly responsible for action, and ventral pathway for perception. So postural control might be more sensitive to motion than static tilt. This study investigated the effects of motion and tilt of large-visual-stimulus on postural control and on the perception of stimulus-tilt and self-tilt.
A photo slide was projected onto a large hemispheric screen (2 m in diameter). Initially the slide was upright for 10 sec, then presented with a tilt (0 − ±20 deg; + : cw, − : ccw). Right after or 10 sec after presenting tilted stimulus, subjects responded the perceived stimulus-tilt or self-tilt. The center of body was measured using force-plate for 70 sec. These three measures were collected in different sessions. Subjects kept standing upright and seeing the center of screen throughout a trial. Results showed that even when subjects didn't see the rotating motion, their center of body, as well as stimulus-tilt or self-tilt perception, was affected by static tilt with the same amount and time course as rotating motion presented. Information about vertical or horizontal axis in natural-scene might have strong effects on postural control.