Prominent role of the spinal central pattern generator in the recovery of locomotion after partial spinal cord injuries.
Journal of Neuroscience. 2008-04-09; 28(15): 3976-3987
DOI: 10.1523/JNEUROSCI.5692-07.2008
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The re-expression of hindlimb locomotion after complete spinal cord injuries
(SCIs) is caused by the presence of a spinal central pattern generator (CPG) for
locomotion. After partial SCI, however, the role of this spinal CPG in the
recovery of hindlimb locomotion in the cat remains mostly unknown. In the present
work, we devised a dual-lesion paradigm to determine its possible contribution
after partial SCI. After a partial section of the left thoracic segment T10 or
T11, cats gradually recovered voluntary quadrupedal locomotion. Then, a complete
transection was performed two to three segments more caudally (T13-L1) several
weeks after the first partial lesion. Cats that received intensive treadmill
training after the partial lesion expressed bilateral hindlimb locomotion within
hours of the complete lesion. Untrained cats however showed asymmetrical hindlimb
locomotion with the limb on the side of the partial lesion walking well before
the other hindlimb. Thus, the complete spinalization revealed that the spinal CPG
underwent plastic changes after the partial lesions, which were shaped by
locomotor training. Over time, with further treadmill training, the asymmetry
disappeared and a bilateral locomotion was reinstated. Therefore, although
remnant intact descending pathways must contribute to voluntary goal-oriented
locomotion after partial SCI, the recovery and re-expression of the hindlimb
locomotor pattern mostly results from intrinsic changes below the lesion in the
CPG and afferent inputs.