Dr. Leyton is a Professor in the Department of Psychiatry at McGill University. The focus of his research is the neurobiology of drug self-administration, addiction, and addiction-related neuropsychiatric disorders. Most of these studies are conducted on people and benefit from (i) a clinical research unit where drugs can be administered under safe conditions, and (ii) functional neuroimaging facilities at the Montreal Neurological Institute (PET, MRI). Dr. Leyton’s research has been particularly interested in the following questions. First, what are the acute effects of abused substances in the human brain, particularly within the mesocorticolimbic dopamine pathways? Second, what is the behavioural significance of drug-induced dopamine release in humans? Third, can repeated drug use produce long-lasting effects in the human brain, for example, conditioning, sensitization, and cross-sensitization? And since individual differences in drug-induced behavioural and neurobiological responses can be identified, he is studying (i) factors that might account for these differences, and (ii) whether the differences might influence susceptibility to addiction and addiction-related co-morbid conditions.