The role of central and peripheral vision in postural control during walking.

Three hypotheses have been proposed for the roles of central and peripheral vision in the perception and control of self-motion: (1) peripheral dominance, (2) retinal invariance, and (3) differential sensitivity to radial flow. We investigated postural responses to optic flow patterns presented at different retinal eccentricities during walking in two experiments. Oscillating displays of radial flow (0 degree driver direction), lamellar flow (90 degrees), and intermediate flow (30 degrees, 45 degrees) patterns were presented at retinal eccentricities of 0 degree, 30 degrees, 45 degrees, 60 degrees, or 90 degrees to participants walking on a treadmill, while compensatory body sway was measured. In general, postural responses were directionally specific, of comparable amplitude, and strongly coupled to the display for all flow patterns at all retinal eccentricities. One intermediate flow pattern (45 degrees) yielded a bias in sway direction that was consistent with triangulation errors in locating the focus of expansion from visible flow vectors. The results demonstrate functionally specific postural responses of both central and peripheral vision, contrary to the peripheral dominance and differential sensitivity hypotheses, but consistent with retinal invariance. This finding emphasizes the importance of optic flow structure for postural control regardless of the retinal locus of stimulation.