Nitrous Oxide Neuroimaging

Inclusion Criteria: * have none of the specific exclusion criteria * have a valid email address and valid phone number throughout the study * free from any non-MRI compatible implants Exclusion Criteria: * are pregnant or attempting to conceive * body mass index (BMI) \> 35 * significant memory impairment or hearing loss * sleep apnea * chronic pain or frequently taking pain medication (including tramadol) * any severe or poorly-controlled medical problem (hypertension, diabetes) * neurologic or psychiatric disease, including anxiety, and depression * severe cardiac disease * history of methylenetetrahydrofolate reductase (MTHFR) deficiency or variant mutation, as assessed by personal report * recent ear or eye surgery * being claustrophobic * have metal implants or non-removable metal piercings * having a history of adverse reaction to anesthetics * daily alcohol or heavy alcohol use; history of alcohol abuse * current daily smoker * regular or recent marijuana use (including prescribed/medical marijuana) * illicit drug use, i.e., street drugs * regularly taking: antiepileptics, antidepressants, anti-psychotics, antihistamines, anti-anxiety medication, stimulants, or sleep-aids