Body sway induced by depth linear vection in reference to central and peripheral visual field

Purpose. A significant correlation between the magnitude of linear vection and the degree of body sway induced by a visual stimulus perceived as movin g in depth was previously described (Jpn J Physiol 49: 417-424, 1999). The purpose of this study was to examine the role of the central and peripheral visual fields in inducing vection and body sway. Methods. Ten healthy volu nteer students who had no vestibular or neurological disorders served as su bjects. A depth optokinetic stimulus (DOKS) was projected onto a head-mount ed display (HMD) and was perceived to move in depth. Different amounts of t he central or peripheral visual field were masked independently. The magnit ude of the linear vection induced by the DOKS was evaluated by verbal asses sment and compared with the magnitude of induced body sway. Body sway was m onitored by a video-motion-analyzer that recorded the movement of the head, shoulder, hip, knee and ankle. Results. The magnitude of vection was corre lated with the frequency of DOKS and also with the amplitude of body sway ( r=0.74), When the central visual field was restricted by 10 to 30%, there w as almost no change in the induced body sway and vection, However, when cen tral occlusion was greater than 40%, depth perception and induced body move ment were greatly reduced. With increasing amounts of peripheral field occl usion from 50 to 90%, there was a greater reduction of both vection and bod y sway. Conclusion. Vection is strongly correlated with body movement, and vection and body sway were more dependent on stimulation of the peripheral visual field.