Objective: To use resting state functional connectivity (FC) as a biomarker of synaptic modulation by repetitive transcranial magnetic stimulation (rTMS) in paradigms intended to improve memory and learning. Ancillary outcomes include the effects of rTMS on the interaction between the explicit implicit memory systems. Study population: Healthy adult volunteers Design: The study contains two experiments. Experiment 1 is designed to establish the number of rTMS sessions required to produce a meaningful change in resting parieto-hippocampal FC in healthy subjects. Experiment 2 will replicate a prior experiment which used rTMS to enhance the explicit memory system in healthy subjects, and look for potential effects on the implicit system. This intervention will be contrasted with a negative control condition (vertex stimulation) in a between-groups design. Outcome measures: The primary outcome measure is the change in FC produced by serially applied rTMS and improvement in explicit memory. We will explore whether enhancement of the explicit system has effects on resting state connectivity in the implicit system and whether white matter integrity predicts changes in FC in healthy subjects.
INCLUSION CRITERIA: Experiments 1 and 2: Healthy individuals Age 18-50 (inclusive) English speaking and writing Experiment 3: Age 18-50 (inclusive) English speaking and writing History of mild to moderate TBI Performance 1 standard deviation below age-adjusted population norms on the CVLT-2 within the past year from the date of visit. EXCLUSION CRITERIA: Any current major neurological or psychiatric disorder such as (but not limited to) stroke, Parkinson disease, Alzheimer disease, schizophrenia or major depression History of seizure Medications acting on the central nervous system Ferromagnetic metal in the cranial cavity or eye, implanted neural stimulator, cochlear implant, or ocular foreign body Implanted cardiac pacemaker or auto-defibrillator or pump Non-removable body piercing Claustrophobia Inability to lie supine for 1 hour Pregnancy, nursing, or plans to become pregnant during the study. Members of the NINDS Behavioral Neurology Unit (BNU) For Experiment 2: Participation in Experiment 1