Inclusion Criteria:  Women of child bearing age cannot be pregnant or trying to become pregnant Ability to tolerate small, enclosed spaces without anxiety Ability and willingness to give informed consent to participate No history of neurological disorder Right handed English speaking  Exclusion Criteria:  Are left-handed Are younger than 18 or older than 50 years old Women who are pregnant, suspect they are pregnant, or are attempting to become pregnant Have metal anywhere in the head, excluding the mouth Have a pacemaker, deep brain stimulator, vagus nerve stimulator or any other medically implanted device Have cochlear hearing implants Are taking GABAergic, NDMA-receptor antagonist, or other drug known to influence neural receptors Have any of the below conditions that would put participants at increased risk of having a seizure: a personal or family history of seizure/epilepsy, taking prescription drugs that lower the threshold for seizures, recent history of excessive alcohol consumption, history of alcohol addiction/dependence, recent history of recreational drug use, history of drug addiction/dependence Have been diagnosed with any of the following: a stroke, brain hemorrhage, brain tumor, encephalitis, multiple sclerosis, Parkinson's disease or Alzheimer's disease, depression in the past 6 months, attention deficit disorder, schizophrenia, manic depressive (bipolar) disorder, normal pressure hydrocephalus or increased intra-cranial pressure, diabetes requiring insulin treatment, any serious heart disorder or liver disease Have had a migraine in the past month MRI specific exclusion criteria: Any relevant history of open-heart surgery, artificial heart valve, brain aneurysm surgery, braces or extensive dental work, cataract surgery or lens implant, or artificial limb or joint. History of foreign metallic object in the body such as bullets, BB's, pellets, shrapnel, or metalwork fragments. Claustrophobia, have uncontrollable shaking, or cannot lie still for one hour.