CNS injury, including traumatic brain injury (TBI), spinal cord injury (SCI), stroke, and certain neurodegenerative diseases, can lead to permanent and devastating functional losses. Under normal circumstances, neurons in the mature central nervous system (CNS: brain, spinal cord, eye) cannot re-establish their connections after injury, nor can intact cells grow new connections to compensate for those that have been lost. As a result of this, victims of traumatic injury, stroke or neurodegenerative diseases can suffer permanent and often devastating losses in movement, sensation, bodily functions, and thinking.