Mapping knee torques evoked by intraspinal microstimulation
The purpose of this study is to evaluate the feasibility of motor system neural prostheses based on intraspinal microstimulation. The isometric torque generated about the knee joint by microstimulation of the lumbar spinal cord were mapped systematically in acute experiments on adult cats anesthetized with α-chlorolose. Electrode locations in the ventral horn generated the largest torques, and there was both mediolateral and dorsoventral segregation of the torque responses in the rostrocaudal plane. Smaller torques were generated by microstimulation in the dorsal part of the spinal cord, and these responses were strongly dependent on stimulus frequency. These results indicate that microstimulation of the spinal cord allows selective activation of knee flexors and extensors by both direct and indirect activation of spinal motoneurons. Anatomically defined segregation between the innervation of flexors and extensors was reproduced in these mapping experiments.