Laboratory of Functional Morphology, University of Antwerp, Universiteitsplein 1, 2610 Antwerp, Belgium.
Laboratory of Functional Morphology, University of Antwerp, Universiteitsplein 1, 2610 Antwerp, Belgium.
J Biomech. 2021 May 24;121:110418. doi: 10.1016/j.jbiomech.2021.110418. Epub 2021 Apr 9.
Running inevitably causes the animal trunk to undulate. The consequential head rotations have to be stabilised in space for a steady gaze and an accurate sense of self-motion for balance. The ecology and anatomy of the species determine the necessity to stabilise the head in yaw, pitch, and roll direction. Terrestrial lizards, running with a sprawled body posture, are especially prone to undulations in the horizontal (yaw) plane. Measurements on an experimental oscillation platform show that Acanthodactylus pardalis lizards stabilise their head less in pitch direction (54% stabilisation) than in yaw and roll direction (66% and 64% stabilisation, respectively). Because we performed these experiments in darkness, the lizards based their head stabilisation on vestibular information. Hence, we hypothesised that their vestibular system is less sensitive in pitch direction than in yaw and roll direction. Yet, this was not confirmed by a detailed Fluid-Structure Interaction model of the membranous labyrinth, which showed that not pitch sensitivity (88% of yaw sensitivity), but roll sensitivity (73% of yaw sensitivity) is the lowest. So why is the head stabilisation in darkness almost as good in roll direction as in yaw direction? While this may be due to neurological nonlinearities, it seems worth noticing that the moment of inertia is lowest in roll direction due to the elongated head shape. Hence, less torque is needed to stabilise a head rotation in roll direction than in the other two directions.
奔跑不可避免地会导致动物躯干起伏。为了保持稳定的注视和准确的自身运动感以维持平衡，头部的随之转动必须在空间中得到稳定。物种的生态和解剖结构决定了头部在偏航、俯仰和滚动方向上稳定的必要性。以伸展身体姿势奔跑的陆生蜥蜴尤其容易在水平（偏航）平面上产生波动。在实验振荡平台上的测量表明，变色蜥蜴（Acanthodactylus pardalis）在俯仰方向上对头部的稳定程度（54%的稳定度）不如在偏航和滚动方向上（分别为 66%和 64%的稳定度）。由于我们在黑暗中进行了这些实验，蜥蜴基于前庭信息来稳定头部。因此，我们假设它们的前庭系统在俯仰方向上的敏感度不如在偏航和滚动方向上。然而，对膜迷路的详细流固耦合模型的研究并未证实这一点，该模型表明，不是俯仰敏感度（偏航敏感度的 88%），而是滚动敏感度（偏航敏感度的 73%）最低。那么，为什么在黑暗中头部的稳定在滚动方向上几乎与在偏航方向上一样好？虽然这可能归因于神经非线性，但值得注意的是，由于头部形状的拉长，滚动方向上的转动惯量最低。因此，与其他两个方向相比，在滚动方向上稳定头部转动所需的扭矩较小。
