Timing dependent synergies between motor cortex and posterior spinal stimulation in humans.

Pairs of stimuli that alter nervous system function typically target the motor system alone or the sensorimotor convergence in cortex. In humans undergoing clinically indicated surgery we tested a paired brain and spinal cord stimulation paradigm that we developed in rats to target sensorimotor convergence in the cervical spinal cord. Arm and hand muscle responses to paired stimulation were six times larger than brain or spinal cord stimulation alone and more selective to the targeted muscles when applied to the posterior but not anterior spinal cord. The paired stimulation effect was independent of the degree of myelopathy, suggesting that it could be applied as therapy in people affected by spinal cord injury.