During testing sessions, the strength of the pointer and little fingers in each hand will be determined through the use of very brief electrical pulses. There also will be transcranial magnetic stimulation (TMS) and 1 Hz TMS. The researchers will place one or two wire coils on the patient's scalp and make marks on the scalp which will be removed at the end of the session. During the TMS, a brief electrical current is passed through the coil, creating a magnetic pulse that stimulates the brain. Patients will hear a click sound and feel a snapping sensation on the skin. They may also feel and see small twitches in the hand muscles, and the fingers or wrist may move. There will be a total of about 300 magnetic stimuli, at a rate of 10 pulses per minute. Patients will also have an electromyogram (EMG), a procedure recording electrical activity in the muscles that are activated by electrical or magnetic stimulation. Metal electrodes will be attached to the skin over the muscle. During the EMG, patients will be asked to tense certain muscles slightly. Depending on the group a patient is assigned to, he or she may be asked to use the right index finger by using voluntary muscle movement, electrical stimulation, his or her imagination, electrical stimulation of a different hand muscle, or voluntary movements immediately followed by repetitive TMS.