In their Nature paper, Claudia Kathe et al. with Grégoire Courtine’s group at EPFL used a mouse model of chronic spinal cord injury to study effects of epidural electrical stimulation (EES) previously observed in humans receiving EES during rehabilitation. They identified a group of neurons that are necessary and sufficient for recovery of walking following spinal cord injury. They used NeuroNexus A4x16-Poly2-5mm-23s-200-177-A64 probes and the SmartBox Pro™ to achieve single-unit recordings in the mouse spinal cord during electrical and optical stimulation.