Objective The Behavioral Neurology Unit studies the human brain systems underlying learning and adaptation with the ultimate goal of finding interventions to make these processes more efficient. We are interested in whether repetitive transcranial magnetic stimulation (rTMS) can alter functional connectivity (FC) and behavioral efficiency in two memory networks in the brain: the hippocampal network, which supports the storage and retrieval of recallable facts, concepts, and events, and the striatal network, which supports the storage and retrieval of skills and habits. Additionally, because these networks interact behaviorally and can interfere with each other, an important question is whether neuromodulation of one network changes connectivity and efficiency in the other network. Pilot data from our group suggest that exogenous stimulation of one network causes it to expand its range of FC and co-opt resources from the other, which is a potential mechanism for the observed behavioral interaction. This study is designed to test a) whether rTMS- modulates within-network FC and memory supported by that network, and b) whether this also causes FC and behavioral changes in the other network. Study population: Healthy Volunteers Design This study contains four between-subjects experiments and is a mixed inter-/intra subject design. Experiment 1 will use nominally excitatory stimulation targeting the hippocampal network to increase FC within the hippocampal network. We also expect to increase FC between the hippocampal and striatal networks, increased declarative memory, and a possible decrease in procedural, learning. Experiment 2 will use excitatory stimulation targeted to the striatal network. We expect this to cause stronger within- network FC in the striatal network, increased FC between the hippocampus and the striatal network and concomitant behavioral effects. Experiments 3 and 4 will be similar except that we will target nominally inhibitory stimulation to these networks and look for the inverse results. FC will be measured under resting and task-activated conditions and active rTMS will be compared to vertex sham. Outcome measures The primary outcome measure is the change in FC produced by rTMS within the targeted network. Between-network FC changes and corresponding memory changes will be secondary outcomes. Exploratory measures will include correlations between individual cognitive differences (questionnaires and NIH Toolbox scores), and our primary and secondary outcome measures.
- INCLUSION CRITERIA: - Age 18-40 (inclusive) 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, such as those that lowers the seizure threshold such as neuroleptics, beta lactams, isoniazid, metronidazole; benzodiazepines, tricyclic or other antidepressants; or prescription stimulants. - 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 2 hours - Pregnancy, or plans to become pregnant during the study. - Members of the NINDS BNU - Subjects that received rTMS under protocol 17-N-0055 are excluded in order avoid learning effects from previously being exposed to the same behavioral tasks - Subjects who have contraindications to MRI (we will follow the NMR Center guidelines for MR safety). Some of the exclusions are: - Have non-MRI compatible metal in the body, such as a cardiac pacemaker, brain stimulator, shrapnel, surgical metal, clips in the brain or on blood vessels, cochlear implants, artificial heart valves or ferromagnetic fragments in the eye or oral cavity as these make having an MRI unsafe. - Unable to lie flat on the back for the expected length of the experiment (2 hours). - Have an abnormality on the brain imaging or neurologic examination not related to the diagnosis. - Non-removable body piercing or - Pregnancy (urine pregnancy test)