Weighting to visual information provided at the various floor oscillation timings while standing

Abstract

  We investigated weighting to visual information provided at the various floor oscillation timings while standing. Subjects were 13 healthy young adults. First, subjects adapted to the floor oscillation with eyes closed in 0.5 Hz frequency and 2.5 cm amplitude. Next, floor oscillation was applied to the subjects for 2 minutes with visual stimulation at the following oscillation points: (1) anterior and (2) posterior reversal points, the midpoints of (3) forward translation and (4) backward translation. In each condition, visual stimulation with white and black vertical stripes was presented for 40 ms by opening a shutter-goggle. Mean speed of the center of foot pressure was significantly smaller in (2), (3) and (4) than in eyes closed condition. Negative peak of event-related potential was observed near the anterior reversal point in all conditions. Positive peak (P200) amplitude of visual evoked potential observed 200 ms after visual stimulation onset was significantly larger in (4) than (1) and (2). A significant negative correlation was recognized between P200 amplitude and SD of head sway (r = 0.58). It is considered that in all visual stimulation conditions, attention was directed to somatosensory stimulation arisen in a close timing with the anterior reversal point, as well as in the condition with eyes closed. The weighting to visual information was the largest in (4), and it would be closely correlated with phase delay of the head movement against the floor movement. Weighting to the sensory information during floor oscillation would be dynamically modulated according to the utility.