Gaze strategies for avoiding obstacles: Differences between young and elderly subjects

Keller Chandra, Sandra; Bockisch, Christopher J.; Dietz, Volker; Hegemann, Stefan C.A.; Straumann, Dominik; van Hedel, Hubertus J.A.

doi:10.1016/j.gaitpost.2011.05.022

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Volume 34, Issue 3 , Pages 340-346, July 2011

Gaze strategies for avoiding obstacles: Differences between young and elderly subjects

Sandra Keller Chandra
- Research Lab, Spinal Cord Injury Center, Balgrist University Hospital, Forchstrasse 340, CH-8008 Zurich, Switzerland
- Corresponding author. Tel.: +41 0 44 386 3741; fax: +41 0 44 386 3731.
Christopher J. Bockisch
- Neurology Department, Zurich University Hospital, Switzerland
- ENT Department, Zurich University Hospital, Switzerland
- ZIHP, Zurich Center for Integrative Human Physiology, Switzerland
- Ophthalmology Department, Zurich University Hospital, Switzerland
Volker Dietz
- Research Lab, Spinal Cord Injury Center, Balgrist University Hospital, Forchstrasse 340, CH-8008 Zurich, Switzerland
- ZIHP, Zurich Center for Integrative Human Physiology, Switzerland
Stefan C.A. Hegemann
- ENT Department, Zurich University Hospital, Switzerland
- ZIHP, Zurich Center for Integrative Human Physiology, Switzerland
Dominik Straumann
- Neurology Department, Zurich University Hospital, Switzerland
- ZIHP, Zurich Center for Integrative Human Physiology, Switzerland
Hubertus J.A. van Hedel
- Research Lab, Spinal Cord Injury Center, Balgrist University Hospital, Forchstrasse 340, CH-8008 Zurich, Switzerland
- ZIHP, Zurich Center for Integrative Human Physiology, Switzerland
- Pediatric Rehab Research Group, Rehabilitation Center Affoltern am Albis, University Children's Hospital, Zurich, Switzerland

Received 21 October 2010; received in revised form 9 May 2011; accepted 24 May 2011. published online 22 June 2011.

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.

Keywords: Gaze-behaviour, Video-oculography, Obstacle-avoidance, Treadmill, Age-comparison