Multi-joint movement of the cat hindlimb evoked by microstimulation of the lumbosacral spinal cord.

Microstimulation of the lumbosacral spinal cord may be an effective tool for the restoration of locomotion after spinal cord injury. To examine this possibility, complex coordinated multi-joint hindlimb movements were evoked by electrical stimulation with sine waveform modulation using a single microelectrode positioned in the L5-S1 spinal cord. Four types of hindlimb movement (flexion, extension, abduction, and adduction) were identified, and their stimulation locations were mapped onto cross-sectional drawings of L5-S1 spinal cord following histological examination of electrode tracks in the cord. Hindlimb flexion was evoked without abduction/adduction at many locations in the dorsal part of the L5-S1 spinal cord, whereas extension was evoked with abduction/adduction in the ventral part of the cord. Bilateral reciprocal lifting of the hindlimb was evoked by implanting two microelectrodes (one on each side) in the spinal cord. This study indicates that functional hindlimb movements can be elicited by activating a small number of sites in lumbosacral spinal cord.