Clinical Research Directory

Inclusion Criteria: * Adults aged 21-35. * No contraindications to MRI or PET scanning. * Right-handed. * Fluent to speak, read, and understand English. Exclusion Criteria: * Adults unable to consent * Contraindications to fMRI scanning and PET scanning (including the presence of a cardiac pacemaker or pacemaker wires, metallic particles in the body, vascular clips in the head or previous neurosurgery, prosthetic heart valves, claustrophobia) * Inability to lie motionless in the scanner * Pregnancy, seeking or suspecting pregnancy, or breastfeeding * History of major head trauma * Intracranial lesion * Cardiovascular disorders, including heart disorders or high blood pressure \[\>155/95\] * Breathing problems such as severe asthma, emphysema, or pulmonary disease * Bleeding disorder, or use of anticoagulants * Bladder obstruction, urinary problems, or history of impaired elimination * Known kidney or liver problems * Past severe COVID-19 infection * Intestinal blockage * Raynaud syndrome * Anemia * Peripheral nerve injury * Diabetes * Glaucoma * Current or recent use of medications (neurological or psychiatric) affecting brain function * Current or past history of major medical, neurological, or psychiatric condition * Current or past history of chronic pain (assessed at the discretion of PI) * Current smoker * Body mass index above 35 * Research-related radiation exposure exceeds current Radiology Department guidelines * Lack of current health insurance coverage * Employed under the direct supervision of the investigators conducting the research * Unwilling or unable to cooperate with breathing maneuvers required during the gas challenge * Respiratory or cardiac limitations to breathing at 20 L/min