Abstract
Purpose: During upright stance condition, vision is known to have an important role in maintaining posture. Central vision is essential for details and motion perception while peripheral vision is primarily specialized for motion perception. However, little is known about their respective roles for postural control in optical flow conditions. In the present study, different visual field areas were stimulated to examine the roles of central and peripheral vision in the control of posture. Methods: Body sway amplitude (BSA) and instability index (II; velocity RMS) were recorded in a group of 19 healthy young adults maintaining upright stance while immersed in a full-immersive virtual environment. The visual stimulation was a 3D tunnel, either static or moving sinusoidaly in the anterior-posterior direction. There were nine visual field conditions: four central conditions (4, 7, 15 and 30°); four peripheral conditions (central occlusions of 4, 7, 15 and 30°); and a full visual field condition. The virtual tunnel respected all the aspects of a real physical tunnel (i.e. stereoscopy and size increase with proximity). Results: Results showed no significant effect of visual field on postural reactivity for the static condition. By contrast, dynamic visual flow reveals a significant increase of postural reactivity when stimulating peripheral visual field (wider than 7°) compared to central. There was no significant difference between the peripheral and full visual field conditions. Conclusions: Under static conditions, central and peripheral vision appear to have equal importance for the control of stance when using a stimulus that equally stimulates these areas. In the presence of an optic flow, peripheral vision has a crucial role in the control of stance, since it is responsible for a compensatory sway, whereas central vision may have an accessory role related to spatial orientation.
NSERC-Essilor Research Chair, CFI, FRSQ.