Previous authors have proposed two basic hypotheses about the factors that form the basis of locomotor rhythms in walking insects: sensory feedback only or sensory feedback together with rhythmic activity of small neural circuits called central pattern generators (CPGs). Here we focus on the latter. Following this concept, to generate functional outputs, locomotor control must feature both rhythm generation by CPGs at the level of individual joints and coordination of their rhythmic activities, so that all muscles are activated in an appropriate pattern. This work provides an in-depth analysis of an aspect of this coordination process based on an existing network model of stick insect locomotion. Specifically, we consider how the control system for a single joint in the stick insect leg may produce rhythmic output when subjected to ascending sensory signals from other joints in the leg. In this work, the core rhythm generating CPG component of the joint under study is represented by a classical half-center oscillator constrained by a basic set of experimental observations. While the dynamical features of this CPG, including phase transitions by escape and release, are well understood, we provide novel insights about how these transition mechanisms yield entrainment to the incoming sensory signal, how entrainment can be lost under variation of signal strength and period or other perturbations, how entrainment can be restored by modulation of tonic top-down drive levels, and how these factors impact the duty cycle of the motor output.

以前的作者提出了关于构成行走昆虫运动节律基础的因素的两个基本假设：仅感觉反馈或感觉反馈连同称为中枢模式发生器 (CPG) 的小神经回路的节律活动。这里我们重点讨论后者。遵循这个概念，为了产生功能性输出，运动控制必须以 CPG 在单个关节水平上的节律生成和它们的节律活动的协调为特征，以便所有肌肉都以适当的模式被激活。这项工作基于现有的竹节虫运动网络模型，对这种协调过程的一个方面进行了深入分析。具体来说，我们考虑了当受到来自腿部其他关节的上升感觉信号时，竹节虫腿中单个关节的控制系统如何产生有节奏的输出。在这项工作中，所研究关节的核心节奏生成 CPG 组件由受一组基本实验观察约束的经典半中心振荡器表示。虽然这种 CPG 的动力学特征，包括逃逸和释放引起的相变，但我们提供了关于这些转变机制如何产生对传入感觉信号的夹带的新见解，在信号强度和周期的变化下夹带如何丢失或其他扰动，如何通过调节自上而下的强直驱动水平来恢复夹带，以及这些因素如何影响电机输出的占空比。所研究关节的核心节律生成 CPG 组件由受一组基本实验观察约束的经典半中心振荡器表示。虽然这种 CPG 的动力学特征，包括逃逸和释放引起的相变，但我们提供了关于这些转变机制如何产生对传入感觉信号的夹带的新见解，在信号强度和周期的变化下夹带如何丢失或其他扰动，如何通过调节强直自上而下的驱动水平来恢复夹带，以及这些因素如何影响电机输出的占空比。所研究关节的核心节律生成 CPG 组件由受一组基本实验观察约束的经典半中心振荡器表示。虽然这种 CPG 的动力学特征，包括逃逸和释放引起的相变，但我们提供了关于这些转变机制如何产生对传入感觉信号的夹带的新见解，在信号强度和周期的变化下夹带如何丢失或其他扰动，如何通过调节强直自上而下的驱动水平来恢复夹带，以及这些因素如何影响电机输出的占空比。