Magnetic Resonance Spectroscopy Studies of Acute Hypoxic and Hyperoxic Breathing in Healthy Volunteers

Inclusion Criteria: * Male or female individuals age between 18 and 40 years old * BMI between 19 and 29 kg/m2 * Having capacity to consent to the study Exclusion Criteria: * Under 18 or over 40 Family history of psychiatric illness among first degree relatives (parents, siblings, or children) * Delirium secondary to medical illness * Any contraindication to MR scan, including claustrophobia, pregnancy, etc. * Medical condition that might endanger the subject during or after a blood draw (e.g. hemophilia) * Significant medical or neurological illness * Prior high altitude pulmonary edema (HAPE) or high-altitude cerebral edema (HACE) diagnosis Born at altitudes greater than 2,100 m (\~7,000 ft) Systemic disease with or without any functional limitation; including controlled hypertension controlled diabetes without systemic effects any cardiac conditions with or without functional limitation, such as, coronary artery disease or valve disease Pregnancy determined by urine pregnancy test, detecting presence of human chorionic gonadotropin (hCG), less than six weeks postpartum, or planning to conceive during the study period. Women who are not willing to receive serum pregnancy tests Active smoking and tobacco chewers. Volunteers may be enrolled if they quit smoking for more than 1 year. Excess alcohol use: more than ½ L/day of wine consumption or equivalent Any current medication use except oral contraceptives. Living in areas that are more than 1,200 m (\~4,000 feet), or have traveled to areas that are more than 1,200 m for more than four days within the last 2 months Anemia, as defined by hemoglobin \< 10g/dL Abnormal hemoglobin (e.g. presence of hemoglobin S) Evidence of apnea or other sleeping disorders Evidence of asthma Lower respiratory infection within the last 30 days Not willing to have blood drawn from an arm vein each test day of the study Claustrophobia (inability to tolerate MRI scan or wear a facemask) Currently enrolled in another research study Facial abnormalities that would preclude proper use of a face mask Hb\<12