Effect of central vs. peripheral optic flow stimuli on postural responses revealed by surface electromyography

While retinal optic flow (OF) is considered a major cue for self-motion and postural stability, it is still debated the relative importance of central vs peripheral vision in visuo-postural responses. Psychophysical studies, by assessing the body sway in response to OF stimuli give more importance to visual periphery as source of compensatory postural responses, while the central vision would play an accessory role. Aim of this study was to verify the different influence of central vs peripheral optic flow stimulation on the activation of lower limb postural muscles: bilateral tibialis anterior and gastrocnemius medialis. Surface EMG was recorded in 24 male and female participants while radial (expansion and contraction) OF stimuli were presented either in a central or peripheral region of a wide screen. The activity of the right tibialis anterior was the most affected by OF stimuli. We found an interaction of sex by muscle in favour of male subjects (78%). The majority of the subjects had a greater postural response for either central or peripheral stimulation, meaning that the influence of visual field region on visuo-postural balance may be subject-specific, probably depending on other stimulus parameters