Mulavara Ajitkumar P, Bloomberg Jacob J
National Space Biomedical Research Institute, Bobby R. Alford Department of Otorhinolaryngology and Communicative Sciences, Baylor College of Medicine, Houston, TX 77030, USA.
J Vestib Res. 2002;12(5-6):255-69.
The goal of the present study was to determine how the multiple, interdependent full-body sensorimotor subsystems respond to a change in gaze stabilization task constraints during locomotion. Nine subjects performed two gaze stabilization tasks while walking at 6.4 km/hr on a motorized treadmill: 1) focusing on a central point target; 2) reading numeral characters; both presented at 2 m in front at the level of their eyes. While subjects performed the tasks we measured: temporal parameters of gait, full body sagittal plane segmental kinematics of the head, trunk, thigh, tibia and foot, accelerations along the vertical axis at the head and the tibia, and the vertical forces acting on the support surface. We tested the hypothesis that with the increased demands placed on visual acuity during the number recognition task, subjects would modify full-body segmental kinematics in order to reduce perturbations to the head in order to successfully perform the task. We found that while reading numeral characters as compared to the central point target: 1) compensatory head pitch movement was on average 22% greater despite the fact that the trunk pitch and trunk vertical translation movement control were not significantly changed; 2) coordination patterns between head and trunk as reflected by the peak cross correlation between the head pitch and trunk pitch motion as well as the peak cross correlation between the head pitch and vertical trunk translation motion were not significantly changed; 3) knee joint total movement was on average 11% greater during the period from the heel strike event to the peak knee flexion event in stance phase of the gait cycle; 4) peak acceleration measured at the head was significantly reduced by an average of 13% in four of the six subjects. This was so even when the peak acceleration at the tibia and the transmission of the shock wave at heel strike (measured by the peak acceleration ratio of the head/tibia and the time lag between the tibial and head peak accelerations) remained unchanged. Taken together these results provide further evidence that the full body contributes to gaze stabilization during locomotion, and that its different functional elements can be modified online to contribute to gaze stabilization for different visual task constraints.
本研究的目的是确定多个相互依存的全身感觉运动子系统在运动过程中如何应对注视稳定任务约束的变化。九名受试者在电动跑步机上以6.4公里/小时的速度行走时执行两项注视稳定任务：1）聚焦于中央点目标；2）阅读数字字符；两者均在其眼睛水平前方2米处呈现。当受试者执行任务时，我们测量了：步态的时间参数、头部、躯干、大腿、胫骨和足部的全身矢状面节段运动学、头部和胫骨沿垂直轴的加速度以及作用在支撑面上的垂直力。我们检验了以下假设：在数字识别任务中，随着对视敏度要求的提高，受试者会改变全身节段运动学，以减少对头部的扰动，从而成功完成任务。我们发现，与中央点目标相比，阅读数字字符时：1）尽管躯干俯仰和躯干垂直平移运动控制没有显著变化，但补偿性头部俯仰运动平均大22%；2）头部俯仰与躯干俯仰运动之间的峰值互相关以及头部俯仰与躯干垂直平移运动之间的峰值互相关所反映的头部与躯干之间的协调模式没有显著变化；3）在步态周期站立相从足跟触地事件到膝关节最大屈曲事件期间，膝关节总运动平均大11%；4）六名受试者中有四名受试者头部测量的峰值加速度平均显著降低了13%。即便胫骨处的峰值加速度以及足跟触地时冲击波的传播（通过头部/胫骨的峰值加速度比以及胫骨和头部峰值加速度之间的时间滞后测量）保持不变，情况也是如此。综合这些结果提供了进一步的证据，表明全身在运动过程中有助于注视稳定，并且其不同的功能元件可以在线修改，以有助于在不同视觉任务约束下实现注视稳定。
