06 Feb Brain-Reward Circuit Both Under and Over Responsive in Addiction and Gambling
MedicalResearch.com Interview with:
Guillaume Sescousse, PhD
Donders Centre for Cognitive Neuroimaging
with collaborators Maartje Luijten, PhD,
and Arnt Schellekens, MD PhD
MedicalResearch.com: What is the background for this study? What are the main findings?
Response: People with an addiction process rewards in their brain differently from people who are not addicted. However, whether this is associated with “too much” or “too little” brain activity is an open question. Indeed, past research has produced conflicting findings.
In order to get a reliable answer, we have combined 25 studies investigating brain reward sensitivity in more than 1200 individuals with and without addiction to various substances such as alcohol, nicotine or cocaine but also gambling. By analyzing the brain images from these studies, we have discovered an important difference in brain activity between expecting a reward and receiving a reward. Compared with non-addicted individuals, individuals with substance or gambling addiction showed a weaker brain response to anticipating monetary rewards. This weaker response was observed in the striatum, a core region of the brain reward circuit, possibly indicating that individuals with an addiction have relatively low expectations about rewards. In contrast, this same region showed a relatively stronger response to receiving a reward in individuals with substance addiction compared with non-addicted individuals. Many addiction rehab centres, such as Avante, offer targeted addiction relief strategies to help a specific person with their addiction.
This stronger response possibly indicates a stronger surprise to getting the reward, and is consistent with low expectations. This same effect was not found among people addicted to gambling.
MedicalResearch.com: What should readers take away from your report?
Response: We believe that there are two main take-home messages.
The first one is about our main finding: the so-called brain reward circuit is under-responsive to anticipating rewards but over-responsive to receiving rewards in individuals with substance addiction compared with non-addicted individuals.
The second main message is about the power of meta-analyses: even though the past 15 years of brain imaging research on addiction have produced conflicting results, combining these studies in a single meta-analysis unveiled a clear pattern of brain response.
MedicalResearch.com: What recommendations do you have for future research as a result of this study?
Response: The results of our meta-analysis are most compatible with the learning-deficit theory of addiction: weaker activation during reward anticipation might reflect an impaired ability to predict upcoming rewards, while increased activity upon reward outcome might in turn reflect increased surprise and so-called prediction error. However this remains a speculative interpretation. It is related to the typical reverse inference problem in brain imaging: since each brain region is involved in many cognitive processes, we cannot directly infer from brain activity which cognitive process is impaired. Careful experimental designs will be needed in order to test more specifically test the learning-hypothesis put forward by our results.
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None of the authors have any disclosures to report.
Luijten M, Schellekens AF, Kühn S, Machielse MWJ, Sescousse G. Disruption of Reward Processing in Addiction An Image-Based Meta-analysis of Functional Magnetic Resonance Imaging Studies. JAMA Psychiatry. Published online February 01, 2017. doi:10.1001/jamapsychiatry.2016.3084
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