The participant sits in a chair with electrodes attached to the muscles that control movement in a finger on the right hand. Reaction time is tested as described in experiment 1. Then, transcranial magnetic stimulation (TMS) is used to test the activity of the brain's motor cortex (the part of the brain that controls movement). For TMS, an insulated wire coil is placed on the subject's scalp. A brief electrical current is passed through the coil, creating a magnetic pulse that travels through the scalp and skull and causes small electrical currents in the brain cortex. The stimulation may cause twitching of the right hand or arm or produce a mild snapping sensation on the scalp. During the stimulation, the electrical activity of muscles in the right hand is recorded on a computer. Following the TMS, DC stimulation is applied, as described in experiment 1. The stimulation begins at a low level and is followed by repeat TMS and DC stimulation at increasingly higher levels. This continues until there is a clear effect on the muscle response to the magnetic pulses, or until the stimulation becomes uncomfortable. At the end of the electrical stimulation, reaction time is tested again.