The Rat Lumbosacral Spinal Cord Adapts to Robotic Loading Applied During Stance

Abstract

cord adapts to robotic loading applied during stance. J Neurophysiol 88: 3108–3117, 2002; 10.1152/jn.01050.2001. Load-related afferent information modifies the magnitude and timing of hindlimb muscle activity during stepping in decerebrate animals and spinal cord– injured humans and animals, suggesting that the spinal cord mediates load-related locomotor responses. In this study, we found that step-ping on a treadmill by adult rats that received complete, midthoracic spinal cord transections as neonates could be altered by loading the hindlimbs using a pair of small robotic arms. The robotic arms applied a downward force to the lower shanks of the hindlimbs during the stance phase and measured the position of the lower shank during stepping. No external force was applied during the swing phase of the step. When applied bilaterally, this stance force field perturbed the hindlimb trajectories so that the ankle position was shifted downward during stance. In response to this perturbation, both the stance an