Lateral dynamic balance reactions to circular translation of the visual field.

Lateral sway of subjects in spontaneous dynamic balance conditions on a seesaw platform was measured during a visual stimulation monocularly produced by a rotating glass covered with a prism membrane. Prism rotation induced the perception of a circular translation of the whole visual field and an ocular pursuit movement. Therefore, the retinal slip that occurs in normal pursuit was cancelled. Strong stereotyped postural reactions were observed in a direction that depended upon both the vertical visual field deviation and the eye stimulated: upper position of the right visual field induced a leftward sway resulting from an extension of the right hemibody; symmetrical reactions occurred for the left stimulation. The results suggest that the postural reactions recorded depend on the isolated oculomotor activity and, in addition, on retinal afferences corresponding to the temporal crescent of the stimulated side, which orientates the postural reaction on the homolateral lower limb muscles.