Is the recovery of stepping following spinal cord injury mediated by modifying existing neural pathways or by generating new pathways? A perspective.

The recovery of stepping ability following a spinal cord injury may be achieved by restoring anatomical connectivity within the spinal cord. However, studies of locomotor recovery in animals with complete spinal cord transection suggest that the adult mammalian spinal cord can acquire the ability to generate stepping after all descending input is eliminated and in the absence of neuronal regeneration. Moreover, rehabilitative gait training has been shown to play a crucial role in teaching existing spinal pathways to generate locomotion and appropriately respond to sensory feedback. This brief review presents evidence that neural networks in the mammalian spinal cord can be modulated pharmacologically and/or with task-specific behavioral training to generate weight-bearing stepping after a spinal injury. Further, the role that spinal learning can play in the management of humans with spinal cord injury is discussed in relation to interventions that are designed primarily to enhance neuronal regeneration.