To establish the extent to which BIIB014, following 8 to 12 consecutive days of dosing at selected dose levels, occupies the brain's A2A receptors. Receptor occupancy will be assessed by PET scanning using a radiolabelled tracer.

Subjects will be enrolled sequentially into cohorts of 2 to 4 subjects. PET scan results will determine the actual number of cohorts enrolled and the BIIB014 dose given to each subject. Since all enrolled subjects will be receiving BIIB014, this study is being listed as a 1-arm, Single Group study (actual study design is dose escalation).

Participating subjects will be required to reside in the clinical unit for 10 to 14 consecutive days. Participants will receive 1 oral dose of BIIB014 daily for 8 to 12 consecutive days. During the study, subjects will undergo 2 PET scans and 1 MRI. Frequent blood sample for pharmacokinetic assessments will also be performed.

Inclusion Criteria:

• BMI between 18.0 and 29.0 kg/m2
• Willing to abstain from caffeine-containing products from 1 week prior to dosing until discharge from unit.
• Willing and able to practice effective contraception until 2 months following last dose of study drug.

Exclusion Criteria:

• History of severe allergic reactions or clinically significant allergies.
• History of malignancy, excluding adequately treated basal cell carcinoma.
• History of any clinically significant disease.
• History of claustrophobia or any condition incompatible with MRI/PET scanning.
• History of any exposure to ionizing radiation, with the exception of dental x-rays, within the 12 months prior to dosing.
• Serious infection within the 4 weeks prior to dosing.
• HbA1c > 6%, positive for Hepatitis C or Hepatitis B, presence of HIV or known exposure to HIV, positive G6PD assay, or any other clinically significant abnormal laboratory parameters at Screening.
• Abnormal supine or standing blood pressure or orthostatic hypotension.
• Any prior treatment with antipsychotic medications, dopamine antagonists, or dopaminergic agonists.
• Treatment with any other investigational drug within 3 months prior to dosing.
• Treatment with any prescription medications within 4 weeks prior to dosing.
• History of drug or alcohol abuse within 1 year prior to dosing.
• Current smoker or any tobacco use within 3 months prior to dosing.
• Heavy caffeine consumption within 4 weeks prior to dosing.