P.3.021 - Brain responses to beer reward: do alcohol consumption levels matter?

Abstract

Background Alcohol use is prevalent during emerging adulthood [1]. Most studies investigating reward processing in alcohol users have used alcohol pictures [2] or monetary rewards [3], which are secondary reinforcers. In the current study, we developed a new paradigm based on the well-known Monetary-Incentive-Delay task, in which we crucially used beer sips as a primary reinforcer. Three different phases can be distinguished; the anticipation of a potential beer reward, the outcome signalling whether the beer reward was obtained, and the delivery of the sip of beer itself. The aims of the current study were to identify the brain activation patterns related to all three phases, and to investigate potential modulations by individual differences in alcohol consumption levels. For the latter purpose, three groups will be compared; light drinkers, at-risk drinkers and dependent drinkers. We hypothesized that reward-related brain areas, such as the striatum, insula and the ventromedial prefrontal cortex, would be more active in the beer than in the water condition across all three phases. Moreover, we hypothesized that the dependent group would show the most activation in the beer>water contrasts, followed by the at-risk group and the light drinkers. Methods The sample consisted of 150 beer drinking males between the age of 18 and 25. The groups were defined using AUDIT scores [4]; light 15, combined with a MINI-interview to confirm dependence in the last group. The participants were all beer-drinking students. All participants underwent a fMRI session in which they completed the modified MID task. The sip of beer or water (3ml) was delivered through a tube placed on the tongue. fMRI data was preprocessed and analyses using SPM8. Results Whole brain analyses revealed that participants showed increased activation in the medial prefrontal cortex (mPFC) and the orbito-frontal cortex (OFC) during the anticipation of a sip of beer compared to water. During the outcome phase, increased activation was found in the inferior frontal gyrus, the motor and visual cortex. During the actual delivery of a sip of beer compared to baseline, increased activation was revealed in the somatosensory cortex, the OFC, the mPFC, cerebellum, amygdala and caudate. Whole brain analyses investigating differences between the three groups revealed no significant results. Conclusions The results show that anticipating and receiving a sip of beer activates a number of brain regions partly overlapping with the reward circuitry. However, in contrast to our hypothesis, no differences were found between the groups of drinkers. These results suggest that reward processing of a primary reinforce may be not be as relevant as expected for explaining individual differences in drinking behaviour [5], as different types of drinkers seem to attribute the same rewarding value to beer across different phases of reward processing. We will extend the current findings by performing more statistical tests as well as region-of-interest analyses and using a continuous measure of alcohol consumption. Eventually, this will give us a better understanding of the rewarding value of alcohol consumption with the final aim to predict future hazardous drinking patterns.