Development of Optimal Sensory Feedback Strategies to Maximize Function After Tetraplegia

The goal of this clinical trial is to learn more about how stimulating the nerves involved in sensation (either in the limbs or in the brain) can be used to restore sensation in participants who have a spinal cord injury. Participants in this study will have already been enrolled in the "Reconnecting the Hand and Arm to the Brain (ReHAB)" study, and received small electrodes in a part of the brain that is involved in sensing touch and pressure in the hand. The ReHAB study participants will also have received electrodes around the nerves in their arm. In this clinical trial, participants will receive two types of electrical stimulation:

* Intracortical microstimulation (ICMS) which involves sending small electrical pulses to the part of the brain that processes sensation. * Peripheral nerve stimulation (PNS) which involves sending small electrical pulses to the nerves in the arm that transmit sensations from the hand.

Researchers will try different patterns of stimulation for both ICMS and PNS and study how the participants perceive the sensations from the different stimulation patterns. The researchers will also study how combining ICMS and PNS affects the perceived sensations.