Enhancing Interhemispheric Disinhibition Between Motor Cortices Using Bilateral Brain Stimulation

This study will determine whether stimulation of the right side of the brain with repetitive transcranial magnetic stimulation (rTMS) followed by stimulation of the left side with theta burst stimulation (TBS) can temporarily change brain activity and improve hand movements in subjects more than has recently been achieved with rTMS alone.

For rTMS, a wire coil is held on the patient's scalp. A brief electrical current is passed through the coil, creating a magnetic pulse that stimulates the brain. The subject hears a click and may feel a pulling sensation on the skin under the coil. There may be a twitch in the muscles of the face, arm or leg. The subject may be asked to tense certain muscles slightly or perform other simple actions. The effect of TMS on the muscles is detected with small metal disk electrodes taped to the skin of the arms or legs. This study uses two kinds of rTMS. In one (Hz rTMS), magnetic pulses are given once per second for a period of 20 minutes; in the other (TBS), a series of pulses are given in bursts, each lasting 2 seconds, for a period of 3 minutes.

Healthy normal volunteers between 18 and 55 years of age may be eligible for this study. Participants undergo the following procedures during three visits to the NIH Clinical Center:

Visit 1:

Participants receive either real or sham rTMS applied on the right side of the brain followed by real or sham TBS applied on the left side of the brain. In addition, subjects undergo the following:

" Pinch force: Subjects press a wedged instrument between the thumb and index finger as hard as they can during several trials every 10 seconds.

" Speed tapping: Subjects press a key on a computer keyboard as quickly as possible for 10 seconds, repeated for several trials.

" Simple reaction time: Subjects respond as quickly as possible to a "go" signal presented on a computer monitor by performing a quick wrist movement.

" Electromyography: Subjects' muscle activity is recorded using electrodes (small metal disks) filled with conductive gel and taped to the skin over the muscle.

Visits 2 and 3

Visit 2 is scheduled for one day after visit 1, and visit 3 is one week after visit 1. Participants do not have brain stimulation during these two visits, but they have TMS measurements, behavioral measurements, and electromyography (EMG) to see if the brain stimulation done during the first visit is still present after a period of time.

At all three visits, participants comp...