Brain Control of Blinking

This study will use transcranial magnetic stimulation (TMS) to study how the brain controls movement of muscles in the face-in particular, those involved in eye blinking. TMS is a procedure that activates areas of the brain with magnetic pulses that travel through the scalp and the skull. Healthy normal volunteers 21 years of age and older may be eligible for this study. They must be free of any serious medical illness, have no neurological or psychiatric disorders or history of seizures, and must not be taking any medications that can affect nervous system function. Participants will undergo TMS and the electrical activity in muscles activated by the stimulation will be recorded. For TMS, an insulated wire coil is placed on the patient's scalp, and a brief electrical current is passed through the coil. This creates a magnetic pulse that travels through the scalp and skull and causes small electrical currents in the outer part of the brain. If the coil is placed over a nerve that controls muscles, there may be a twitch in the muscles, sometimes large enough to move the face. In other cases, there may be a feeling of movement or tingling sensation in the face. Stimulation over the muscles on the side of the head may cause some discomfort there or twitching of the jaw. During the stimulation, subjects may be asked to tense certain muscles slightly or perform other simple actions. Electrical activity of the muscles activated by the stimulation is recorded. This is done with both metal electrodes taped to the skin over the muscle and with fine needle electrodes inserted into the muscles around the eyes. The study usually takes less than 3 hours, with frequent breaks. If more time is required, the study will be broken into more than one session.