Participants will undergo two different procedures in four separate sessions. One procedure (cortical excitability) involves taking either levetiracetam or placebo (a look-alike inactive substance) and having transcranial magnetic stimulation (TMS). The other procedure (pinch-training related changes) involves taking levetiracetam or placebo, doing a motor exercise called pinch training, and having transcranial magnetic stimulation. For TMS, a very brief electrical current is passed through an insulated coil wire placed on the scalp. The magnetic pulse travels through the scalp and skull, causing small electrical currents in the cortex that may cause muscle, hand, or arm twitching or it may affect movements or reflexes. During the study, subjects may be asked to make movements, do simple tasks or tense muscles. Electrical activity of the muscles will be recorded using electrodes taped to the skin over the muscle. For the pinch training, the subject makes a brief, brisk pinch after each beat of a metronome every two seconds and then completely relaxes the hand until the next beat.