Keep looking ahead? Re-direction of visual fixation does not always occur during an unpredictable obstacle avoidance task
Keep looking ahead? Re-direction of visual fixation does not always occur during an unpredictable obstacle avoidance task
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DOI：
10.1007/s00221-006-0598-0
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发表时间：
2007-01-01
影响因子：
2
通讯作者：
Duysens, Jacques
中科院分区：
文献类型：
--
作者：
Marigold, Daniel S.;Weerdesteyn, Vivian;Duysens, Jacques
关于环境的视觉信息，特别是诸如障碍物等关键物体的固定，对于安全移动至关重要。然而，在障碍物突然出现的不可预测的情况下，不知道是否需要障碍物和/或着陆区域的中央视觉，或者周边视觉是否足够。我们研究了在跑步机行走过程中，视觉注视是否从前方注视的物体转向突然出现的障碍物。此外，我们研究了肌肉活动的发病，以避免障碍和扫视的眼睛和头部运动转移固定之间的时间关系。8名女性（平均值+/- SD;年龄= 24.8 +/- 2.3岁）参与了本实验。有两种视觉条件：一种是中央视觉条件，参与者固定在跑步机上连接到桥上的两个障碍物上，另一种是周边视觉条件，参与者固定在两步前的物体上。有两种障碍物释放条件：只有左脚前方的障碍物被释放，或者任何一只脚前方的障碍物都可以被释放。只有当障碍物在左脚前方被释放时的试验才被分析，使得两种障碍物条件的差异在于是否存在选择哪只脚跨过障碍物的选择。障碍物被随机释放的三个阶段之一，在步骤周期对应于可用的响应时间在219和462毫秒之间。我们监测眼睛和头部运动沿着与肌肉活动和空间脚参数。视觉条件下的任务表现没有差异。结果表明，扫视很少发生（< 18%的试验），并且当存在时，在肢体抬高的肌肉活动后类似于350 ms开始，通常伴随着向下的头部运动，并且总是指向着陆区域。因此，在行进路径中突然出现的障碍物的周边视觉足以在运动期间成功地避开障碍物：视觉固定通常不会重新定向到障碍物或着陆区域。
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 suffcient. We examined whether there is a re-direction 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 = 24.8 +/- 2.3 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 similar to 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 re-directed to either the obstacle or landing area.