reward to drugs and associated drug stimuli (i.e.., processes of “wanting”) distinct from the neurocircuitry mediating hedonic reward (liking) which may not sensitize over time. Finally, allostatic theory asserts heightened brain reward sensitivity and positive reinforcement characterize the early stages of addiction(18), but reward insensitivity and negative reinforcement underlie the later and more severe stages(18–20). Thus, while some researchers may not agree on the contributions of positive versus negative reinforcement factors underlying addiction(21, 22), there is consensus on the critical need for longitudinal controlled human alcohol response investigation. Human studies in this area have been limited to retrospective patient reports(23), post mortem brain tissue methods(24), or cross-sectional laboratory paradigms(2, 3, 25–29), none of which directly measure alcohol responses in the same individuals over time. The few published test-retest studies of alcohol responses have included only brief between-session intervals with a focus on measurement reliability(30, 31).
