A new age for rehabilitation
In this review we will describe newly developed techniques that are being used to recover levels of motor function after a severe spinal cord injury that have not been observed previously. These new approaches include pharmacological neuromodulation and/or epidural stimulation of the spinal cord circuitries in combination with motor training. By combining the increased levels of excitability of the interneuronal spinal circuitries using these interventions and the ability of the spinal circuitries to interpret and respond appropriately to ongoing complex ensembles of sensory input, the peripheral sensory system can become an effective source for the control of motor function. Similar types of neuromodulation have been shown to enable the brain to regain functional connectivity with the spinal cord circuitries below a clinically complete spinal cord lesion. In fact, some level of voluntary control of movement has been observed in subjects with complete paralysis in the presence of epidural stimulation. The biological mechanisms thought to underlie the recovery of motor function after a severe spinal cord injury are based on decades of research on a wide range of animal models. Fortunately the extensive conservation of neural mechanisms of motor control has provided a window for gaining considerable insight into the mechanisms of recovery of motor function in humans.