Effects of rTMS on Human Brain Activity

Inclusion Criteria: * Age restrictions: between 18-35 years old * Use of effective method of birth control for women of childbearing capacity. * Willing to provide informed consent. Exclusion Criteria: * Current or recent (within the past 6 months) substance abuse or dependence, excluding nicotine and caffeine (urine test) * Current serious medical illness (self-report) * History of seizure except those therapeutically induced by ECT (childhood febrile seizures are acceptable and these subjects may be included in the study), history of epilepsy in self or first degree relatives, stroke, brain surgery, head injury, cranial metal implants, known structural brain lesion, devices that may be affected by rTMS or MRI (pacemaker, medication pump, cochlear implant, implanted brain stimulator) * Subjects are unable or unwilling to give informed consent * Diagnosed any Axis I DSM-IV disorder (MINI, DSM-IV) Subjects with a clinically defined neurological disorder including, but not limited to: * Any condition likely to be associated with increased intracranial pressure * Space occupying brain lesion. * History of stroke. * Transient ischemic attack within two years. * Cerebral aneurysm. * Dementia. * Parkinson's disease. * Huntington's disease. * Multiple sclerosis. * Increased risk of seizure for any reason, including prior diagnosis of increased intracranial pressure (such as after large infarctions or trauma), or currently taking medication that lowers the seizure threshold * Subjects with cochlear implants * Subjects not willing to tolerate the confinement associated with being in the MRI scanner * Women who are pregnant or breast-feeding (urine test)