Niemeier Miriam, Jeschke Manon, Dürr Volker
Department of Biological Cybernetics, Faculty of Biology, Bielefeld University, Bielefeld, Germany.
Center for Cognitive Interaction Technology, Bielefeld University, Bielefeld, Germany.
Front Bioeng Biotechnol. 2021 Apr 20;9:628998. doi: 10.3389/fbioe.2021.628998. eCollection 2021.
Multi-legged locomotion requires appropriate coordination of all legs with coincident ground contact. Whereas behaviourally derived coordination rules can adequately describe many aspects of inter-leg coordination, the neural mechanisms underlying these rules are still not entirely clear. The fact that inter-leg coordination is strongly affected by cut thoracic connectives in tethered walking insects, shows that neural information exchange among legs is important. As yet, recent studies have shown that load transfer among legs can contribute to inter-leg coordination through mechanical coupling alone, i.e., without neural information exchange among legs. Since naturalistic load transfer among legs works only in freely walking animals but not in tethered animals, we tested the hypothesis that connective lesions have less strong effects if mechanical coupling through load transfer among legs is possible. To do so, we recorded protraction/retraction angles of all legs in unrestrained walking stick insects that either had one thoracic connective cut or had undergone a corresponding sham operation. In lesioned animals, either a pro-to-mesothorax or a meso-to-metathorax connective was cut. Overall, our results on temporal coordination were similar to published reports on tethered walking animals, in that the phase relationship of the legs immediately adjacent to the lesion was much less precise, although the effect on mean phase was relatively weak or absent. Lesioned animals could walk at the same speed as the control group, though with a significant sideward bias toward the intact side. Detailed comparison of lesion effects in free-walking and supported animals reveal that the strongest differences concern the spatial coordination among legs. In free walking, lesioned animals, touch-down and lift-off positions shifted significantly in almost all legs, including legs of the intact body side. We conclude that insects with disrupted neural information transfer through one connective adjust to this disruption differently if they experience naturalistic load distribution. While mechanical load transfer cannot compensate for lesion-induced effects on temporal inter-leg coordination, several compensatory changes in spatial coordination occur only if animals carry their own weight.
多足运动需要所有腿进行适当协调并同时与地面接触。虽然从行为学得出的协调规则能够充分描述腿间协调的许多方面，但这些规则背后的神经机制仍不完全清楚。在拴系行走的昆虫中，胸神经索切断会强烈影响腿间协调，这一事实表明腿间的神经信息交换很重要。然而，最近的研究表明，腿间的负载转移仅通过机械耦合就能促进腿间协调，即无需腿间的神经信息交换。由于腿间自然的负载转移仅在自由行走的动物中起作用，而在拴系动物中不起作用，我们测试了这样一个假设：如果通过腿间负载转移进行机械耦合是可能的，那么神经索损伤的影响就会减弱。为此，我们记录了未受约束的竹节虫在行走时所有腿的前伸/后缩角度，这些竹节虫要么切断了一条胸神经索，要么接受了相应的假手术。在受损动物中，要么切断前胸与中胸之间的神经索，要么切断中胸与后胸之间的神经索。总体而言，我们关于时间协调的结果与已发表的关于拴系行走动物的报告相似，即紧邻损伤部位的腿之间的相位关系精确性大大降低，尽管对平均相位的影响相对较弱或不存在。受损动物能够以与对照组相同的速度行走，不过明显向完整一侧有侧向偏差。对自由行走和支撑状态下动物的损伤效应进行详细比较发现，最显著的差异在于腿间的空间协调。在自由行走时，受损动物几乎所有腿的着地和离地位置都有显著变化，包括完整身体一侧的腿。我们得出结论，通过一条神经索破坏神经信息传递的昆虫，如果经历自然的负载分布，会以不同方式适应这种破坏。虽然机械负载转移无法补偿损伤对腿间时间协调的影响，但只有当动物承载自身重量时，才会出现一些空间协调方面的补偿性变化。
