Mapping Brain Glutamate in Humans: Sex Differences in Cigarette Smokers

Inclusion Criteria: 1. Self-identified as only male or female 2. Age 18-45 years (children \<18 years will be excluded due to low prevalence of conventional cigarette smoking; female participants \>45 years of age will be excluded to avoid effects of perimenopause and menopause in women; male participants \>45 years of age will be excluded as well to ensure that male and female groups are matched on age 3. English fluency demonstrated by verbal skills sufficient to participate in a conversation, including the ability to ask and answer questions at a level that assures adequate understanding of the study (a comprehension quiz will be given) 4. Right handedness (evaluated using the Edinburgh Inventory) 5. Generally in good health without cardiovascular, hepatic, renal, or autoimmune diseases, diabetes, or cancer 6. Must have smoked for ≥1 year 7. Must endorse inhaling while smoking 8. Must smoke ≥10 cigarettes per day 9. Must have expired CO \>10 ppm and urinary cotinine ≥100 ng/ml at screening/intake 10. Fulfillment of DSM-5 criteria for Tobacco Use Disorder Exclusion Criteria: 1. Seeking treatment for nicotine dependence within 3 months of screening 2. Medical condition that may compromise safety (based on history, physical exam) 3. Neurological disorder that would compromise compliance and/or informed consent 4. Major psychiatric disorder (e.g., Major Depression, Schizophrenia, Bipolar Disorder) per DSM-5 MINI 5. Current drug use disorders other than Tobacco Use Disorder (as defined in DSM-5) 6. Recent use of cocaine, opiates, benzodiazepines, or amphetamines as shown by urine test at the screening or testing sessions 7. Smoke marijuana \>3X/week (self-report) or positive marijuana urine test on a scan day (positive at screening allowed) 8. Use of tobacco in forms other than cigarettes (e.g., snuff, chewing tobacco, e-cigarettes) \>10 days in the month before screening 9. Preference for menthol cigarettes, given sex differences in the effect of menthol on the rate of nicotine entry into the brain 10. Pregnancy or nursing 11. Presence in the body of metal that would compromise safety during MRI 12. Claustrophobia 13. Any other condition that would compromise safety