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 rot ation induced the perception of a circular translation of the whole vi sual field and an ocular pursuit movement. Therefore, the retinal slip that occurs in normal pursuit was cancelled. Strong stereotyped postu ral reactions were observed in a direction that depended upon both the vertical visual field deviation and the eye stimulated: upper positio n of the right visual field induced a leftward sway resulting from an extension of the right hemibody; symmetrical reactions occurred for th e left stimulation. The results suggest that the postural reactions re corded depend on the isolated oculomotor activity and, in addition, on retinal afferences corresponding to the temporal crescent of the stim ulated side, which orientates the postural reaction on the homolateral lower limb muscles. ((C) Academie des sciences/Elsevier, Paris.)