It is known that primates including human regain some locomotor function after a partial spinal cord injury, but the locomotor pattern is different from before the injury. Although these observations have many implications for improving rehabilitative strategies, these mechanisms are not well understood. In this study, we used a common marmoset hemisection SCI model to examine temporal changes in locomotor pattern, in particular, intersegmental coordination of left hindlimb. Marmoset showed loss of detectable function in the left forelimb and hindlimb after left unilateral hemisection of cervical spinal cord. At two weeks after injury, weight-bearing of the left forelimb during locomotion was limited, but the left hindlimb was able to plantar step. Then marmosets showed gradual recovery in walking ability, but kinematics analysis showed differences in the endpoint trajectory and joint angle movement. Furthermore, intersegmental coordination in left hindlimb represented by planar covariation was preserved over time after the injury. Previous studies have reported that planar covariance is disrupted in patients with stroke or SCI, and that improvement in planarity correlates with recovery in walking ability after rehabilitation. In this study, quadrupedal marmosets were able to walk without loss of balance even after SCI; the different balance needs of bipedal and quadrupedal walkers may lead to differences in planar covariation. Our results show that planar covariation was preserved at all time points after the cervical unilateral hemisection.
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