Department for Biological Cybernetics, Faculty for Biology, University of Bielefeld Postfach 100131, D-33501 Bielefeld, Germany.
Integr Comp Biol. 2002 Feb;42(1):165-73. doi: 10.1093/icb/42.1.165.
In the experiments stick insects walk on an inclined substrate such that the legs of one side of the body point uphill and the legs of the other side point downhill. In this situation the vertical axis of the body is rotated against the inclination of the substrate as if to compensate for the effect of substrate inclination. A very small effect has been found when the experiment was performed with animals standing on a tilted platform which shows that the effect depends on the behavioral context. When, however, animals first walked along the inclined surface and then, before measurement, stopped walking spontaneously, a rotation of the body has been observed similar to that in walking animals. In a second experiment it was tested whether the observed body rotation is caused by the change of direction of gravity vector or by the fact that on an inclined surface gravity necessarily has a component pulling the body sideways. Experiments with animals standing on horizontal ground and additional weights applied pulling the body to the side showed similar body rotations supporting the latter idea. In a simulation study it could be shown that the combined activity of proportional feedback controllers in the leg joints is sufficient to explain the observed behavior. This is however only possible if the gain factors of coxa-trochanter joint controller and of femur-tibia joint controller show a ratio in the order of 1 : 0.05 to 1 : 1.8. In order to describe the behavior of animals standing on a tilted platform, a ratio of 1 : 1.7 is necessary. In walking animals, this body rotation requires to change the trajectories of stance and swing movements. The latter have been studied in more detail. During swing, the femur-tibia joint is more extended in the uphill legs. Conversely, the coxa-trochanter joint appears to be more elevated in the downhill legs which compensates the smaller lift in the femur-tibia joint. The results are discussed in the context of different hypotheses.
在实验中，竹节虫在倾斜的基质上行走，使得身体一侧的腿部指向上坡，另一侧的腿部指向下坡。在这种情况下，身体的垂直轴会抵抗基质的倾斜而旋转，好像是在补偿基质倾斜的影响。当实验在倾斜平台上进行时，发现了一个非常小的效应，这表明这种效应取决于行为背景。然而，当动物首先沿着倾斜表面行走，然后在测量前自发停止行走时，观察到了类似于行走动物的身体旋转。在第二个实验中，测试了观察到的身体旋转是否是由重力矢量方向的变化引起的，或者是由于在倾斜表面上，重力必然有一个将身体侧向拉动的分量引起的。在动物站在水平地面上的实验和施加额外重量以将身体拉向一侧的实验中，观察到了类似的身体旋转，支持了后一种观点。在模拟研究中，可以证明腿部关节中比例反馈控制器的组合活动足以解释观察到的行为。然而，只有当coxa-trochanter 关节控制器和 femur-tibia 关节控制器的增益因子显示出 1:0.05 到 1:1.8 的比值时，才是可行的。为了描述站在倾斜平台上的动物的行为，需要 1:1.7 的比值。在行走动物中，这种身体旋转需要改变支撑和摆动运动的轨迹。后者已经被更详细地研究过。在摆动过程中，上坡腿的 femur-tibia 关节伸展得更充分。相反，下坡腿的 coxa-trochanter 关节似乎升高得更多，以补偿 femur-tibia 关节较小的提升力。结果在不同的假设背景下进行了讨论。
