Role of foveal and peripheral visual information in maintenance of postural equilibrium in man.

In a previous report (Amblard & Crémieux, 1976) we demonstrated that the maintenance of postural equilibrium, measured with the subject in Mann's stance on a foam rubber support, was significantly more difficult under stroboscopic rather than normal lighting conditions. The most plausible cause of the difficulty is the subject's loss of visual perception of movement as a result of the stroboscopic lighting. The present study was designed to look at this factor under normal lighting conditions. Also, the relative contributions of foveal and peripheral vision were assessed. During stance, the subjects (5 women and 6 men, aged from 25 to 55 yr.) viewed either a horizontal or a vertical rectangular grating. With horizontal lines, the visual perception of lateral movement is minimized. Lateral acceleration was measured at three anatomical levels: ankles, hips, and head. The horizontal stripe condition was significantly less effective than the vertical stripe one for maintenance of balance, both for measurements at the head level only and for values averaged from all three levels. Balance was significantly impaired with foveal vision alone compared to full vision or to peripheral vision alone, for measurements from each of the three levels. We conclude that the visual perception of movement is a very important factor in the maintenance of the equilibrium, peripheral vision playing the major role, and foveal vision only a supplementary one.