In this undated photo provided by the University of Louisville, from left to right, are Andrew Meas, Dustin Shillcox, Kent Stephenson and Rob Summers, the first four to undergo task-specific training with epidural stimulation at the Human Locomotion Research Center laboratory, Frazier Rehab Institute, as part of the University of Louisville's Kentucky Spinal Cord Injury Research Center, in Louisville Ky. Three years ago, doctors reported that zapping a paralyzed man’s spinal cord with electricity allowed him to stand and move his legs. Now they’ve done the same with three more patients, suggesting their original success was no fluke. (AP Photo/University of Louisville)