This preclinical phase 1 development study in healthy volunteers seeks to identify if low doses of commonly used non-triggering anesthetic agents might have clinical utility for modulating emotional memory processing and to understand the nature of the brain mechanisms of drug action. Optimally, a drug, dose and brain mechanism of action will be identified that will form the foundation for future use in clinical studies of patients with PTSD.

Inclusion Criteria:

• Healthy adults.
• Between the ages of 18 and 35.

Exclusion Criteria:

• Pregnancy.
• Left-handed.
• Unusual facial anatomy.
• History of esophageal reflux.
• Respiratory problems.
• Central nervous system disorders.
• Cardiovascular problems.
• Kidney disease.
• Diabetes.
• History of Substance abuse.
• History of adverse anesthetic reactions.
• Hepatitis.
• Failure to pass MRI screening questionnaire.
• Fear of small-enclosed spaces.
• Mental illness.
• Non-native English speakers.