The present disclosure provides methods and systems for receiving, with processing circuitry of an implant device, an electrical signal from a free tissue graft attached to a portion of a nerve (e.g., a nerve branch or fascicle) through an electrical conductor in electrical communication with the free tissue graft (e.g., muscle graft), the nerve having reinnervated the free tissue graft. The electrical signal from the free tissue graft has a voltage amplitude of greater than or equal to about 150 microvolts. The processing circuitry stores signal data corresponding to the electrical signal from the free tissue graft in a memory accessible to the processing circuitry.