Objective: Alcohol dependence may be associated with dysfunction of mesolimbic circuitry, such that anticipation of nonalcoholic reward fails to activate the ventral striatum, while alcohol-associated cues continue to activate this region. This may lead alcoholics to crave the pharmacological effects of alcohol to a greater extent than other conventional rewards. The present study investigated neural mechanisms underlying these phenomena.
Methods: 16 detoxified male alcoholics and 16 age-matched healthy volunteers participated in two fMRI paradigms. In the first paradigm, alcohol-associated and affectively neutral pictures were presented, whereas in the second paradigm, a monetary incentive delay task (MID) was performed, in which brain activation during anticipation of monetary gain and loss was examined. For both paradigms, we assessed the association of alcohol craving with neural activation to incentive cues.
Results: Detoxified alcoholics showed reduced activation of the ventral striatum during anticipation of monetary gain relative to healthy controls, despite similar performance. However, alcoholics showed increased ventral striatal activation in response to alcohol-associated cues. Reduced activation in the ventral striatum during expectation of monetary reward, and increased activation during presentation of alcohol cues were correlated with alcohol craving in alcoholics, but not healthy controls.
Conclusions: These results suggest that mesolimbic activation in alcoholics is biased towards processing of alcohol cues. This might explain why alcoholics find it particularly difficult to focus on conventional reward cues and engage in alternative rewarding activities.