 The procedure is the same as for session 1, except subjects receive an infusion of alcohol one session and an infusion of saline salt water the other. Also, subjects undergo positron emission tomography PET scanning during the infusions. For this test, the subject lies on a bed that slides in and out of a doughnut-shaped scanner. A custom-molded mask is used to support the head and prevent it from moving during the scanning. A small amount of radioactive substance called C-11 raclopride is injected through one of the catheters to trace brain dopamine activity. 