Lower Limb Function After Spinal Cord Injury

This study plans to examine plasticity in corticospinal synapses of lower-limb muscles. it has been demonstrated that plasticity elicited at corticospinal synapses in the spinal cord result in enhancements in electromyographic (EMG) and force activity in upper-limb muscles. The first step in this proposal is to determine if synaptic plasticity can be elicited in corticospinal projections targeting lower-limb muscles in humans with SCI. We will also study methods to strengthen corticospinal plasticity to promote recovery of leg clearance during training. We will use two novel strategies to enhance plasticity in corticospinal synapses of lower-limb muscles after SCI: a). administration of an N-methyl-D-aspartate (NMDA) receptor agonist (i.e. D-cycloserine), and b). Combine NMDA-induced corticospinal plasticity with training (2D lower limb training and locomotor training. Corticospinal synaptic plasticity is thought to depend on activation of NMDA receptors and D-cycloserine enhances motor skill behaviors in animals and humans will be enhanced by NMDA-induced corticospinal plasticity. An important strength of this aim is the combination of training and strategies that aimed at enhancing the synaptic efficacy of residual corticospinal projections. Training effects on physiological pathways will be explored and correlated with locomotor function