Modulation of the Parieto-frontal Communication

Background: Research shows that the parietal and prefrontal areas of the brain are involved in short-term memory. Researchers want to look at the effects of transcranial magnetic stimulation (TMS) of these areas on short-term memory and brain activity. They will use functional magnetic resonance imaging (fMRI) to look at brain activity. Objective: To look at the effects of TMS on brain pathways involved in memory. Eligibility: Healthy, right-handed adults ages 18-50 Design: Participants will have 3 or 4 visits at least 1 week apart. They cannot drink alcohol for at least 48 hours before each visit. The screening visit lasts about 1 (Omega) hours. It can be combined with the first testing visit. Screening includes: * Medical history * Physical exam * Neurological exam * Urine tests * Questionnaires about being left or right handed and about their ability to imagine physical activities. The first testing visit lasts about 1 (Omega) hours and includes an MRI. For the MRI, participants lie on a table that slides into a machine. They will lie still or perform simple memory tasks on a computer screen. The second and third testing visits last about 3 hours. Participants will have: * 2 MRIs * TMS: A wire coil is held to the scalp. A brief electrical current passes through the coil to create a magnetic pulse that affects brain activity. They will perform simple memory tasks. * EMG: Small electrodes are taped to the skin to record muscle activity while they rest. After the study, participants will complete a questionnaire about any discomfort they experienced during the study. ...