The first steps after paralysis: Immediate locomotor responses following electrically induced loss and recovery of neuromuscular function

Abstract

Abstract In nature, animals must rapidly regain coordinated locomotion after neuromuscular injury, but the earliest compensatory strategies remain unknown. We addressed this gap using a chronic, implantable kilohertz electrical stimulation (KES) system to reversibly block tibial nerve conduction in freely walking rats, and measuring gait adaptation within seconds of perturbation. KES suppressed gastrocnemius muscle activity and altered ankle and knee kinematics, while indirectly driving compensatory hip motions. Across repeated sessions of nerve block, whole-limb dynamics were increasingly preserved despite altered joint function and dimensional reduction with gait signature analysis revealed reduced differences between Pre-KES and KES cycles with learning. After nerve block removal, limb length initially overshoots baseline, demonstrating a neural adaptive after-effect. These results indicate the nervous system utilizes existing locomotor networks as an immediate compensatory response recruiting proximal joint-driven strategies to stabilize whole-limb mechanics through feedforward strategies when presented with the loss of neuromuscular function.