This study is being done in healthy volunteers to help researchers understand how ABT-614 works in the human body, specifically in the brain. The PET imaging technique can be thought of as a way to take pictures of chemical changes in the brain. To take a PET scan (picture), a substance with low levels of radioactivity (radiotracer) has to be injected when you are in the PET camera. The radiotracer is only radioactive for a short period of time. In this study, PET is being used to measure how the study drug attaches to specific receptors in the brain. The radiotracer used in this study, [11C]-(+)-PHNO, is currently being used for studies in people at the CAMH PET Centre.