Our previous study of cat locomotion demonstrated that lateral displacements of the centre of mass (COM) were strikingly similar to those of human walking and resembled the behaviour of an inverted pendulum (Park et al. 2019 J. Exp. Biol. 222, 14. (doi:10.1242/jeb.198648)). Here, we tested the hypothesis that frontal plane dynamics of quadrupedal locomotion are consistent with an inverted pendulum model. We developed a simple mathematical model of balance control in the frontal plane based on an inverted pendulum and compared model behaviour with that of four cats locomoting on a split-belt treadmill. The model accurately reproduced the lateral oscillations of cats' COM vertical projection. We inferred the effects of experimental perturbations on the limits of dynamic stability using data from different split-belt speed ratios with and without ipsilateral paw anaesthesia. We found that the effect of paw anaesthesia could be explained by the induced bias in the perceived position of the COM, and the magnitude of this bias depends on the belt speed difference. Altogether, our findings suggest that the balance control system is actively involved in cat locomotion to provide dynamic stability in the frontal plane, and that paw cutaneous receptors contribute to the representation of the COM position in the nervous system.

中文翻译：

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在分带式跑步机上进行四足运动时质心的正面动力学

我们之前对猫运动的研究表明，质心 (COM) 的横向位移与人类行走的横向位移惊人地相似，并且类似于倒立摆的行为（Park 等人，2019 J. Exp. Biol. 222, 14。 (doi:10.1242/jeb.198648))。在这里，我们测试了四足运动的额平面动力学与倒立摆模型一致的假设。我们开发了一个基于倒立摆的额平面平衡控制的简单数学模型，并将模型行为与四只在分带式跑步机上运动的猫的行为进行了比较。该模型准确再现了猫 COM 垂直投影的横向振荡。我们使用来自不同分裂带速度比的数据推断实验扰动对动态稳定性限制的影响，有和没有同侧爪子麻醉。我们发现爪子麻醉的效果可以用 COM 感知位置的诱导偏差来解释，这种偏差的大小取决于皮带速度差异。总而言之，我们的研究结果表明，平衡控制系统积极参与猫的运动以提供额平面的动态稳定性，并且爪子皮肤受体有助于表示神经系统中 COM 的位置。