Dorsal column section of the spinal cord was performed under general anesthesia. Each monkey was initially sedated with ketamine hydrochloride (15mg/kg, i.m.) and then maintained at a surgical level of anesthesia with 1-3% isoflurane. The depth of anesthesia was evaluated by the heart and respiration rates, and testing for withdraw reflexes. Rectal body temperature was maintained at 37 – 38.5 °C. Under aseptic conditions, a portion of the cervical spinal cord was exposed, and the dorsal columns were sectioned on one side with a fine pair of surgical scissors at cervical level C4 - C6. The dura was replaced with Gelfilm and covered with Gelfoam. The opening was closed, and the skin sutured. Monkeys were carefully monitored until they were fully recovered from anesthesia, and then returned to their home cage. The monkeys also received antibiotics and analgesics for three days after surgery. Animals’ cage behavior and food intake typically returned to normal shortly after surgery. Further details about surgical procedures can be found in previous publications from the laboratory (Jain et al 1997 (link); Jain et al 2008 (link); Qi et al 2011 (link)).