Dürr Volker
Abteilung für Biologische Kybernetik und Theoretische Biologie, Fakultät für Biologie, Universität Bielefeld, Postfach 10 01 31, 33501 Bielefeld, Germany.
J Exp Biol. 2005 Jun;208(Pt 12):2253-67. doi: 10.1242/jeb.01638.
Appropriate coordination of stepping in adjacent legs is crucial for stable walking. Several leg coordination rules have been derived from behavioural experiments on walking insects, some of which also apply to arthropods with more than six legs and to four-legged walking vertebrates. Three of these rules affect the timing of stance-swing transition [rules 1 to 3 (sensu Cruse)]. They can give rise to normal leg coordination and adaptive responses to disturbances, as shown by kinematic simulations and dynamic hardware tests. In spite of their importance to the study of animal walking, the coupling strength associated with these rules has never been measured experimentally. Generally coupling strength of the underlying mechanisms has been considered constant rather than context-dependent. The present study analyses stepping patterns of the stick insect Carausius morosus during straight and curve walking sequences. To infer strength and efficacy of coupling between pairs of sender and receiver legs, the likelihood of the receiver leg being in swing is determined, given a certain delay relative to the time of a swing-stance (or stance-swing) transition in the sender leg. This is compared to a corresponding measure for independent, hence uncoupled, step sequences. The difference is defined as coupling strength. The ratio of coupling strength and its theoretical maximum is defined as efficacy. Irrespective of the coordination rule, coupling strength between ipsilateral leg pairs is at least twice that of contralateral leg pairs, being strongest between ipsilateral hind and middle legs and weakest between contralateral middle legs. Efficacy is highest for inhibitory rule 1, reaching 84-95% for ipsilateral and 29-65% for contralateral leg pairs. Efficacy of excitatory rules 2 and 3 ranges between 35-56% for ipsilateral and 8-21% for contralateral leg pairs. The behavioural transition from straight to curve walking is associated with context-dependent changes in coupling strength, increasing in both outer leg pairs and decreasing between inner hind and middle leg. Thus, the coordination rules that are thought to underlie many adaptive properties of the walking system, themselves adapt in a context-dependent manner.
相邻腿部迈步的适当协调对于稳定行走至关重要。一些腿部协调规则源自对行走昆虫的行为实验，其中一些规则也适用于腿数超过六条的节肢动物以及四足行走的脊椎动物。这些规则中的三条影响 stance-swing 转换的时间 [规则 1 至 3（按克鲁泽的定义）]。如运动学模拟和动态硬件测试所示，它们能产生正常的腿部协调以及对干扰的适应性反应。尽管它们对动物行走研究很重要，但与这些规则相关的耦合强度从未通过实验测量过。一般而言，潜在机制的耦合强度被认为是恒定的，而非依赖于情境。本研究分析了直走和转弯行走序列中竹节虫 Carausius morosus 的迈步模式。为了推断发送腿和接收腿对之间耦合的强度和功效，在给定相对于发送腿摆动 - 站立（或站立 - 摆动）转换时间的特定延迟的情况下，确定接收腿处于摆动状态的可能性。将此与独立（即未耦合）步序列的相应测量值进行比较。差异被定义为耦合强度。耦合强度与其理论最大值的比率被定义为功效。无论协调规则如何，同侧腿对之间的耦合强度至少是对侧腿对的两倍，在同侧后肢和中肢之间最强，在对侧中肢之间最弱。抑制性规则 1 的功效最高，同侧腿对达到 84 - 95%，对侧腿对达到 29 - 65%。兴奋性规则 2 和 3 的功效在同侧腿对中为 35 - 56%，在对侧腿对中为 8 - 21%。从直走行为到转弯行走的转变与耦合强度的情境依赖性变化相关，外侧腿对的耦合强度增加，内侧后肢和中肢之间的耦合强度降低。因此，被认为是行走系统许多适应性特性基础的协调规则本身也以情境依赖的方式进行调整。
