This is an exploratory study to evaluate the usefulness of fMRI as a biomarker to characterize the response to three centrally active drugs and placebo.

Inclusion Criteria:

• Adult patients, 18 to 45 years of age
• In good general health
• Weight of ≥120 lbs (55 kg) and a body mass index (BMI) between 18 to 30kg/m²
• Males and females with reproductive potential: willing to use a reliable method of contraception

Exclusion Criteria:

• Evidence of clinically significant disease
• Medical or surgical condition that could alter the absorption, metabolism, or elimination of drugs
• Family history of sudden death or ventricular arrhythmia
• History of any psychiatric disorder and/or marked anxiety
• History of glaucoma
• History (including family) of motor tic or diagnosis of Tourette's syndrome
• Active suicide ideation
• Contraindication to MRI