Authors: Daniel S Marigold Vivian Weerdesteyn Aftab E Patla Jacques Duysens
Publish Date: 2006/07/04
Volume: 176, Issue: 1, Pages: 32-42
Abstract
Visual information about the environment especially fixation of key objects such as obstacles is critical for safe locomotion However in unpredictable situations where an obstacle suddenly appears it is not known whether central vision of the obstacle and/or landing area is required or if peripheral vision is sufficient We examined whether there is a redirection of visual fixation from an object fixated ahead to a suddenly appearing obstacle during treadmill walking Furthermore we investigated the temporal relationship between the onset of muscle activity to avoid the obstacle and saccadic eye and head movements to shift fixation Eight females mean ± SD age = 248 ± 23 years participated in this experiment There were two visual conditions a central vision condition where participants fixated on two obstacles attached to a bridge on the treadmill and a peripheral vision condition where participants fixated an object two steps ahead There were two obstacle release conditions only an obstacle in front of the left foot was released or an obstacle in front of either foot could be released Only trials when the obstacle was released in front of the left foot were analyzed such that the difference in the two obstacle conditions was whether there was a choice of which foot to step over the obstacle Obstacles were released randomly in one of three phases during the step cycle corresponding to available response times between 219 and 462 ms We monitored eye and head movements along with muscle activity and spatial foot parameters Performance on the task was not different between vision conditions The results indicated that saccades are rarely made 18 of trials and when present are initiated ∼ 350 ms after muscle activity for limb elevation often accompanied by a downward head movement and always directed to the landing area Therefore peripheral vision of a suddenly appearing obstacle in the travel path is sufficient for successful obstacle avoidance during locomotion visual fixation is generally not redirected to either the obstacle or landing areaThe authors wish to thank Bart Nienhuis for his help This study was supported by a Canada Graduate Scholarship from the Canadian Institutes of Health Research DSM the Organization for Healthcare Research in the Netherlands ZonMW VW and a EU grant Eurokinesis QLK6CT200200151 JD
Keywords: