title: Gaze strategies for avoiding obstacles: Differences between young and elderly subjects.
abstract: Visual input is highly relevant for safely stepping over obstacles. In this study, gaze-behaviour was investigated in elderly, middle-aged and young subjects as they walked on a treadmill repeatedly stepping over obstacles, which approached either on the right or left side. In between obstacle-steps, subjects visually fixated a target N or F located two or four steps ahead on the floor, respectively. An acoustic warning signal announced the obstacles, after which subjects were free to look wherever they wanted. Gaze-movements were measured by video-oculography. Four conditions with 20 obstacles were conducted (two with target N, two with target F). In two conditions, high-precision stepping was investigated by asking subjects to step with minimal foot-clearance over the obstacles, while receiving acoustic feedback about their performance. In the high-precision conditions, more subjects (target N: 70%, F: 81%) turned their gaze on the obstacles and for a longer time than in unrestricted conditions. When fixating on the near target N and unrestricted stepping over the obstacles, significantly more elderly subjects (85%) turned their gaze on the obstacle compared to middle-aged (17%) and young subjects (29%). The elderly turned their gaze earlier and longer on the obstacle than middle-aged or young subjects. Our results reveal a different gaze-behaviour strategy of elderly subjects suggesting a greater dependency on visual inputs.
authors.affiliation: Research Lab, Spinal Cord Injury Center, Balgrist University Hospital, Forchstrasse 340, CH-8008 Zurich, Switzerland. skeller@paralab.balgrist.ch
authors.forename: Sandra
authors.initials: S
authors.lastname: Keller Chandra
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Bockisch
authors.forename: Volker
authors.initials: V
authors.lastname: Dietz
authors.forename: Stefan C A
authors.initials: SC
authors.lastname: Hegemann
authors.forename: Dominik
authors.initials: D
authors.lastname: Straumann
authors.forename: Hubertus J A
authors.initials: HJ
authors.lastname: van Hedel
mesh_terms: D000058:Accidental Falls; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001288:Attention / Q000502:physiology*; D005133:Eye Movements / Q000502:physiology; D005246:Feedback; D005403:Fixation, Ocular / Q000502:physiology*; D005684:Gait / Q000502:physiology*; D006801:Humans; D008875:Middle Aged; D011434:Proprioception / Q000502:physiology; D011597:Psychomotor Performance / Q000502:physiology; D055815:Young Adult