Effect of Transcranial Magnetic Stimulation on Memory

This study will examine the effect of transcranial magnetic stimulation (TMS) on short-term memory in healthy adults. Healthy people use their brains to answer short-term memory questions in a different way than do patients with schizophrenia. Attention and memory deficits in schizophrenia patients significantly hamper their recovery and rehabilitation, yet there are no effective treatments for these impairments. TMS is a method of brain stimulation that may be able to change the electrical activity of the nerve cells of the brain and improve certain brain functions. This study will explore the effect of TMS on memory and perhaps discover brain processes that may be helpful in developing new ways to treat schizophrenia. Healthy volunteers between 18 and 55 years of age, excluding pregnant women, may be eligible for this study. Participants undergo the following tests and procedures: * Medical history, physical examination, blood tests, electrocardiogram (EKG), and urine pregnancy test for women of childbearing age. * Magnetic resonance imaging (MRI) and functional MRI (fMRI). These tests are done in participants who have not had structural and functional MRIs as participants in NIMH's 2-day schizophrenia study within 90 days of entering the current study. MRI is done to locate the place in the brain to simulate with TMS and fMRI is done to look at brain activity while the subject solves short-term memory tasks. Both tests are done at the same session. Before the scan, four vitamin E capsules are taped to the subject's scalp. After the capsules are in place, the subject lies on a stretcher that is moved into the scanner - a narrow cylinder with a strong magnetic field. During the scan, subjects are asked to do some simple tests, such as watching pictures on a screen or pressing buttons in response to numbers they were shown a few seconds earlier. Scanning may take up to 2 hours, but usually lasts between 45 and 90 minutes. * TMS. For this procedure, subjects receive either active TMS or a sham procedure (placebo) that imitates TMS but does not use real electrical stimulation. For TMS, an insulated wire coil is placed on the scalp and a brief electrical current is passed through it. This generates magnetic pulses that travel through the scalp and skull and cause small electrical currents in the cortex, or outer part of the brain. The stimulation may cause muscle twitching in the scalp or face and may also cause small movement of the limbs. During the procedure, electrodes are taped to the scalp to record the electrical activity of the brain while short-term memory is tested. Two tests make up a set. There are a total of six test sets; each set takes about 3 minutes. Five periods of electrical stimulation are delivered before each test set. Each period of stimulation lasts 5 seconds, followed by a 10-second rest period. The stimulation-rest intervals continue until five periods of TMS have been applied. For the memory test, subjects press a key on a computer keyboard as quickly and accurately as possible in a test of their ability to remember a string of numbers, or letters. * Questionnaires. At the beginning and end of the TMS session, participants fill out questionnaires that assess their mood, ability to concentrate, and level of anxiety.