The study aims to examine the combined effects of delta-9-tetrahydrocannabinol (∆-9-THC or THC) and iomazenil on thinking, perception, mood, memory, attention, and electrical activity of the brain (EEG). THC is the active ingredient of marijuana, cannabis, "ganja", or "pot". Iomazenil is a drug that works opposite to drugs like valium. The purpose of this study is to determine whether the administration of iomazenil will alter the effects of THC.