title: The visual control of stepping operates in real time: Evidence from a pictorial illusion.
abstract: Recent studies have suggested important similarities between the visual control of upper and lower limb actions despite the different effectors, time scales, and regions of space associated with the two types of actions. Drawing on previous findings from upper limb studies, we show here that the effect of a Muller-Lyer illusion on stepping amplitude is greatly increased when the target display is occluded as compared to when it is visible during the reaction time period (i.e., brief delay and 3-s delay conditions versus full vision and open-loop conditions). The present results suggest that the control of stepping is mediated by different systems when the target is visible as compared to when it is occluded immediately before movement initiation; when target vision is not available during the reaction time period, the control of stepping is more highly dependent upon a non-veridical, perceptual representation of the target environment. These findings are consistent with the idea that, much like grasping, vision during the reaction time period is critical for the optimal control of stepping; that is, the visual control of stepping operates in real time.
authors.affiliation: School of Health and Human Performance, Dalhousie University, 6230 South Street, , B3H 3J5, Halifax, Nova Scotia, Canada.
authors.forename: Elizabeth M
authors.initials: EM
authors.lastname: McCarville
authors.forename: David A
authors.initials: DA
authors.lastname: Westwood
mesh_terms: D000328:Adult; D001132:Arm / Q000294:innervation / Q000502:physiology; D003463:Cues; D003627:Data Interpretation, Statistical; D005260:Female; D006801:Humans; D007866:Leg / Q000294:innervation / Q000502:physiology; D008297:Male; D009068:Movement / Q000502:physiology*; D009903:Optical Illusions / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology; D014796:Visual Perception / Q000502:physiology*