We investigate a simple model for motor pattern generation that combines central pattern generator (CPG) dynamics with a sensory feedback (FB) mechanism. Our CPG comprises a half-center oscillator with conductance-based Morris–Lecar model neurons. Output from the CPG drives a push–pull motor system with biomechanics based on experimental data. A sensory feedback conductance from the muscles allows modulation of the CPG activity. We consider parameters under which the isolated CPG system has either “escape” or “release” dynamics, and we study both inhibitory and excitatory feedback conductances. We find that increasing the FB conductance relative to the CPG conductance makes the system more robust against external perturbations, but more susceptible to internal noise. Conversely, increasing the CPG conductance relative to the FB conductance has the opposite effects. We find that the “closed-loop” system, with sensory feedback in place, exhibits a richer repertoire of behaviors than the “open-loop” system, with motion determined entirely by the CPG dynamics. Moreover, we find that purely feedback-driven motor patterns, analogous to a chain reflex, occur only in the inhibition-mediated system. Finally, for pattern generation systems with inhibition-mediated sensory feedback, we find that the distinction between escape- and release-mediated CPG mechanisms is diminished in the presence of internal noise. Our observations support an anti-reductionist view of neuromotor physiology: Understanding mechanisms of robust motor control requires studying not only the central pattern generator circuit in isolation, but the intact closed-loop system as a whole.

我们研究了一种简单的运动模式生成模型，该模型将中央模式生成器 (CPG) 动力学与感觉反馈 (FB) 机制相结合。我们的 CPG 包括一个半中心振荡器和基于电导的 Morris-Lecar 模型神经元。 CPG 的输出利用基于实验数据的生物力学驱动推拉电机系统。来自肌肉的感觉反馈电导可以调节 CPG 活动。我们考虑孤立 CPG 系统具有“逃逸”或“释放”动力学的参数，并研究抑制性和兴奋性反馈电导。我们发现，相对于 CPG 电导而言，增加 FB 电导可以使系统对外部扰动更加稳健，但更容易受到内部噪声的影响。相反，相对于 FB 电导增加 CPG 电导会产生相反的效果。我们发现，具有感觉反馈的“闭环”系统比“开环”系统表现出更丰富的行为，而“开环”系统的运动完全由 CPG 动力学决定。此外，我们发现纯粹反馈驱动的运动模式（类似于链反射）仅发生在抑制介导的系统中。最后，对于具有抑制介导的感觉反馈的模式生成系统，我们发现在存在内部噪声的情况下，逃逸和释放介导的 CPG 机制之间的区别会减弱。我们的观察结果支持神经运动生理学的反还原论观点：理解鲁棒运动控制的机制不仅需要研究孤立的中央模式发生器电路，而且还需要研究整个完整的闭环系统。