Neuromechanical Model of Rat Hindlimb Walking with Two-Layer CPGs

Abstract

This work demonstrates a neuromechanical model of rat hindlimb locomotionundergoing nominal walking with perturbations. In the animal, two types of responses toperturbations are observed: resetting and non-resetting deletions. This suggests that the animallocomotor system contains a memory-like organization. To model this phenomenon, we built asynthetic nervous system that uses separate rhythm generator and pattern formation layers toactivate antagonistic muscle pairs about each joint in the sagittal plane. Our model replicates theresetting and non-resetting deletions observed in the animal. In addition, in the intact (i.e., fullyafferented) rat walking simulation, we observe slower recovery after perturbation, which isdifferent from the deafferented animal experiment. These results demonstrate that our model is abiologically feasible description of some of the neural circuits in the mammalian spinal cord thatcontrol locomotion, and the difference between our simulation and fictive motion shows theimportance of sensory feedback on motor output. This model also demonstrates how the patternformation network can activate muscle synergies in a coordinated way to produce stable walking,which motivates the use of more complex synergies activating more muscles in the legs for threedimensionallimb motion.