Abstract
Background: Reinforcement of behavioral responses involves a complex cerebral circuit engaging specific neuronal networks that are modulated by cortical oversight systems affiliated with emotion, memory, judgment, and decision making (collectively referred to in this study as the "extended reward and oversight system" or "reward network"). We examined whether reward-network brain volumes are reduced in alcoholics and how volumes of subcomponents within this system are correlated with memory and drinking history. Methods: Morphometric analysis was performed on magnetic resonance brain scans in 21 abstinent long-term chronic alcoholic men and 21 healthy control men, group-matched on age, verbal IQ, and education. We derived volumes of total brain and volumes of cortical and subcortical reward-related structures including the dorsolateral-prefrontal, orbitofrontal, cingulate cortices, and the insula, as well as the amygdala, hippocampus, nucleus accumbens septi (NAc), and ventral diencephalon. Results: Morphometric analyses of reward-related regions revealed decreased total reward-network volume in alcoholic subjects. Volume reduction was most pronounced in right dorsolateral-prefrontal cortex, right anterior insula, and right NAc, as well as left amygdala. In alcoholics, NAc and anterior insula volumes increased with length of abstinence, and total reward-network and amygdala volumes correlated positively with memory scores. Conclusions: The observation of decreased reward-network volume suggests that alcoholism is associated with alterations in this neural reward system. These structural reward system deficits and their correlation with memory scores elucidate underlying structural-functional relationships between alcoholism and emotional and cognitive processes.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 192-202 |
| Number of pages | 11 |
| Journal | Biological psychiatry |
| Volume | 64 |
| Issue number | 3 |
| DOIs | |
| State | Published - Aug 1 2008 |
Funding
Abstinent long-term chronic alcoholics have volumetric deficits in the brain's extended reward and oversight system. Deficits were most pronounced in right dorsolateral-prefrontal cortex, right anterior insula, right NAc, and left amygdala. This study differs from prior investigations in two principal aspects. First, structures related to processing reward information were considered to be an interconnected and interrelated system, which was treated as a unique group of regions in statistical analyses. Second, correlations associating reward-network morphometry with behavioral tests and drinking history were performed. Memory correlated positively with reward-network volume—particularly the amygdala—and length of abstinence correlated with increased volumes in NAc and anterior insula. The circuitry overseeing reward and aversion is fundamental for normal emotional functioning and its malfunction. The finding that the reward system is altered in alcoholism and is correlated with memory and drinking history argues that a condition predisposes individuals to alcohol dependence, perhaps as a result of a genetic deficit in reward circuitry; that long-term alcoholism damages parts of the brain involved in reward processing and may lead to a cycle of accelerating dependence on alcohol; or both. This work was supported in part by grants from the National Association for Research in Schizophrenia and Depression and the National Institutes of Health National Center for Complementary and Alternative Medicine to NM; the National Institute on Alcohol Abuse and Alcoholism (NIAAA) (Grant Nos. R37-AA07112 and K05-AA00219) and the Medical Research Service of the U.S. Department of Veterans Affairs to MO-B; NIAAA K01-AA13402 to KM; the Fairway Trust to DK; and by the National Center for Research Resources (Grant No. P41RR14075) and the Mental Illness and Neuroscience Discovery Institute. We thank Diane Merritt for assistance in recruiting the research participants. None of the authors report any biomedical financial interest or potential conflicts of interest.
Keywords
- Alcoholism
- MRI
- amygdala
- dorsolateral-prefrontal cortex
- nucleus accumbens
- reward system
ASJC Scopus subject areas
- Biological Psychiatry
