Reward processing in alcoholics and non-alcoholics: A functional magnetic resonance study

Addiction theories posit long-term alterations in reward systems from repeated activation of these areas. Acute administration of addictive substances has been demonstrated to activate the same brain systems as natural rewards. Comparative studies indicate that reward processes can be delineated into appetitive and consummatory phases. Advances in functional neuroimaging allow for further delineation of human reward processes. Consistent with primate studies, these studies demonstrate NAcc activity during anticipation of a reward and MPFC activity after receiving a reward. Regarding addiction, the role of dopamine and reward-related areas has been well documented but often without delineating stages of reward processing. Examining reward as distinct phases may provide a basis for further understanding hypothesized neuroadaptive changes related to addiction. In this study, FMRI is used to probe neural responses to monetary rewards in recently abstinent alcohol-dependent individuals and healthy controls. With regard to anticipation and goal directed behavior, addiction may impact the rewarding value of an addictive substance by altering its incentive salience, leading to increased motivation for an addictive substance at the expense of motivation for other rewards. Alternately, addiction may increase the hedonic value of consuming a drug while attenuating responses to non-drug rewards. Thirty-two alcoholic inpatients and healthy volunteers were scanned while they completed the Monetary Incentive Delay task during which they could win or avoid losing money by responding during a target presentation. Multiple regression and repeated measures ANOVA were conducted for within and between group analyses. Similar but reduced patterns of brain activation were observed in response to monetary incentive cues in both groups. Replicating previous findings, reward anticipation proportionally activated the ventral striatum in both groups, however, in alcoholic inpatients only, prefrontal activation increased with incentive magnitude in both gain and loss valences. These findings suggest that addiction may impact reward responsiveness by altering the saliency of rewarding stimuli without affecting motivational drive, which can potentially impact decision-making processes. If saliency is shifted such that important contextual information is ignored, this may pave the way for addictive behavior where the most motivationally salient aspect is sought out without consideration of potential negative consequences.