Patla A E, Adkin A, Martin C, Holden R, Prentice S
Department of Kinesiology, University of Waterloo, ON., Canada.
Exp Brain Res. 1996 Dec;112(3):513-22. doi: 10.1007/BF00227957.
The characteristics of visual sampling required for successful locomotion over various terrains is the focus of this work. In the first experiment we directly address the role of continuous visual monitoring of the environment in guiding locomotion by allowing the subjects to choose when and where to take a visual sample of the terrain and examine the effects of different terrains on characteristics of visual sampling. Young subjects walked over travel paths of varying difficulties while wearing opaque liquid crystal eyeglasses and pressed a hand-held switch to make the glasses transparent when they needed to sample the environment. Travel time and visual sampling characteristics were recorded. Results show that intermittent sampling (less than 50%) of the environment is adequate for safe locomotion, even over a novel travel path. The frequency, duration and timing of visual samples are dependent on terrain characteristics. Visual sampling of the environment is unaffected by preview restriction of the travel path and is increased when specific foot placement is required and there is a potential hazard in the travel path. In the second experiment we dissociated steering control and obstacle avoidance from specific foot placement and examined visual sampling demands prior to the initiation of the swing phase and during the swing phase. The results show that steering control and obstacle avoidance do influence the visual sampling time, which is scaled to the magnitude of change. Vision was used in a feedforward control mode to plan for and initiate appropriate changes in the swing limb trajectory: its use during the swing phase to provide on-line control was minimal.
在各种地形上成功行走所需的视觉采样特征是本研究的重点。在第一个实验中，我们通过让受试者选择何时何地对地形进行视觉采样，直接探讨了持续视觉监测环境在引导行走中的作用，并研究了不同地形对视觉采样特征的影响。年轻受试者戴着不透明的液晶眼镜在不同难度的行进路径上行走，当需要对环境进行采样时，按下手持开关使眼镜变透明。记录行进时间和视觉采样特征。结果表明，即使在新的行进路径上，对环境进行间歇性采样（少于50%）也足以保证安全行走。视觉采样的频率、持续时间和时机取决于地形特征。对环境的视觉采样不受行进路径预览限制的影响，当需要特定的足部放置且行进路径存在潜在危险时，视觉采样会增加。在第二个实验中，我们将转向控制和避障与特定的足部放置分开，并研究了摆动相开始前和摆动相期间的视觉采样需求。结果表明，转向控制和避障确实会影响视觉采样时间，该时间与变化幅度成比例。视觉在前馈控制模式下用于规划和启动摆动肢体轨迹的适当变化：在摆动相期间用于提供在线控制的情况很少。
