This study will determine: 1) whether learning a task with the dominant hand is accompanied by changes in the area of the brain that controls hand movement, and 2) how the brain is able to make these changes. Previous studies have shown that practicing a motor task can change brain excitability, but it is not known how well brain excitabilities are changed during motor learning. This study will measure changes in activity of the part of the brain that controls hand movement before, during, and after exercising the hand on a response pad.

Healthy normal volunteers between 18 and 40 years of age may be eligible for this study. Candidates who have not been evaluated at NIH within the past year will be screened with a brief interview about their current state of health and clinical and neurological examinations. Participants will undergo the following procedures:

Learning a finger movement/reaction time task

For this procedure, participants sit in front of a computer monitor with the index, middle, ring, and little fingers placed flat on four corresponding buttons of a response pad. They are asked to press one of the four buttons as fast as they can in response to an asterisk displayed on the monitor. The position of the asterisk indicates which button to push. Subjects perform nine sets of 120-button pushes with a 15-minute rest between each set. During the rest period, subjects undergo transcranial magnetic stimulation (described below), which causes twitches in the hand muscles. The electrical activity corresponding to the twitches is recorded by attaching electrodes (small metal disks) to the skin over the hand muscles.

Transcranial magnetic stimulation

For this test, an insulated wire coil is held over the scalp. A brief electrical current passes through the coil, creating a magnetic pulse that electrically stimulates the brain. The subject hears a click and may feel a pulling sensation on the scalp under the coil. The stimulation may also cause twitching in the muscles of the face, arm, or leg. During the stimulation, the subject may be asked to tense certain muscles slightly or perform other simple actions.

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