supply a source of power to move and walk. several such devices are already available for sale, but investigation is still underway as to how they can be made more useful. preliminary studies of epidural spinal cord stimulators for motor complete injuries have demonstrated some improvement, and in some cases to enable walking to some degree bypassing the injury. in 2014 darek fidyka underwent pioneering spinal surgery that used nerve grafts, from his ankle, to 'bridge the gap' in his severed spinal cord and olfactory ensheathing cells (oecs) to stimulate the spinal cord cells. the surgery was performed in poland in collaboration with prof. geoff raisman, chair of neural regeneration at university college london's institute of neurology, and his research team. the oecs were taken from the patient's olfactory bulbs in his brain and then grown in the lab, these cells were then injected above and below the impaired spinal tissue.