2009 Volume 14 Issue 1 Pages 131-139
We aimed to investigate the effects of eccentricity and size of visual field on visually induced postural sway. Optic flow stimuli were presented in a Central Vision (CV) condition and four Peripheral Vision (PV) conditions. In the CV condition, random dots were presented in a circular area (15 deg in radius). In the PV conditions, random dots were presented in the outside of the central area (15 deg in radius) to be a ring (donut) shape. Scaling factors of the donut areas were 0.5, 1.0, 2.0, and 4.0 times of the area of CV condition. Random dots moved laterally or radially back and forth at 0.2 Hz in all conditions. We found head movement in CV condition was stronger than all PV conditions for the lateral motion, and was not significantly different from PV conditions for the radial motion. By applying the cortical magnification factor, the advantage of CV disappeared, but the strength of postural sway decreased with eccentricity in PV conditions. Thus, the mechanism of visual control of posture cannot be accounted for only by retinal eccentricity, retinal size or cortical size, but some other factors or mixed factors should be considered.
