Re‐Expression of locomotion and reflex changes after various types of spinal lesions

Abstract

Locomotion of the hindlimbs is a complex motor act involving several levels of control (supraspinal, sensory, neurochemical) of a spinal circuitry called the Central Pattern Generator (CPG) which essentially generates the basic locomotor pattern. The importance of this CPG is quite evident from experiments showing that cats with a complete spinal section at T13 can gradually recover spontaneous hindlimb locomotion on a treadmill with appropriate locomotor training for a few weeks. The key role played by the CPG, and some reflex changes, in the recovery of locomotion after a complete spinal section is thus inescapable. Is the spinal CPG also involved in the re‐expression of locomotion after partial spinal lesions? A dual lesion paradigm was devised to study this question: hemisection at T10‐T11, locomotor training and then complete section at T13. Our main finding was that, within 24 hours (i.e. the first testing session) following the complete spinal section, treadmill‐trained cats walked remarkably well with the hindlimbs on the treadmill. Thus, the present experiments show that there is also a major functional contribution from the CPG in the recovery of locomotion after partial spinal cord lesions. This highlights the importance of fostering such potential spinal neuroplasticity in rehabilitation strategies by reinforcing both voluntary aspects of locomotion and activity in endogenous spinal circuits.