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Neuroimaging Identifies Brain Regions Possibly Involved in Alcohol Craving
Viewing pictures of alcoholic beverages activates the prefrontal cortex and the anterior thalamus in alcoholics but not in moderate drinkers, report Medical University of South Carolina (MUSC) researchers in the April Archives of General Psychiatry. The research team is the first to use fMRI (functional magnetic resonance imaging) to examine whether alcohol cues stimulate specific brain regions.
"The activated brain regions are known to be associated with attention and regulating emotion and are prominent components of working models of alcohol craving," said National Institute on Alcohol Abuse and Alcoholism Director Enoch Gordis, M.D. "Whether the activity in these areas accompanies craving or is in part responsible for it remains to be determined."
"The regions activated in this study should not yet be interpreted as correlates of craving per se," said lead author Mark S. George, M.D., of the Departments of Psychiatry, Radiology, and Neurology at MUSC. "Our next project uses fMRI scans to measure subjective craving in real time so that we can relate subjective craving temporally to the presentation of visual cues."
For the current study, the researchers recruited eight male and two female alcoholics and an equal number of moderate-drinking (no more than 14 drinks per week) controls matched according to age and gender. The alcoholics met DSM-IV criteria for alcohol dependence, drank an average of seven drinks per drinking day, and drank on about 70 percent of days in the month before testing. They were not severe alcoholics or in treatment at the time of study.
All 20 subjects viewed pictures on a screen while lying on their backs in a 1.5-Tesla MRI scanner. For nine minutes, they were shown a series of photographs of alcoholic beverages followed by a series of nonalcoholic beverages (e.g., coffee, juice, soda) in random order. To heighten their responses to alcohol cues, the subjects were given a sip of an alcoholic beverage before viewing the images. The researchers compared mean group images of brain activity during the alcohol and nonalcohol pictures, exposing in the alcoholic group several brain areas with unique activity during the alcohol pictures.
"Our goals were to learn whether certain brain areas would be activated for the alcohol cues but not the neutral cues and whether brain areas in alcoholics would be activated differently than those of moderate drinkers," said Raymond F. Anton, M.D., a lead study author and Scientific Director of the NIAAA-funded MUSC Alcohol Research Center. "In fact, we saw clearly that certain brain regions in alcoholics activated in response to viewing pictures with alcohol-specific content. It appears that the alcoholics paid greater attention to the alcohol images."
"This work confirms a significant biological and brain component to alcoholism and provides information toward understanding the differences between alcoholics and nonalcoholics," said Dr. George.
Future studies may examine regional brain activity following the administration of naltrexone, a medication believed to reduce alcohol craving, say the authors. Imaging studies are expected eventually to predict risk for both uncontrolled drinking and relapse and to evaluate potential anticraving medications.
Although many alcoholics report craving, an intense desire or "drug hunger" for alcohol, researchers have not arrived at a common understanding of the phenomenon. Most agree that craving involves neuroadaptation--changes in brain cell function resulting from long-term alcohol consumption. Neuroadaptation produces an imbalance in brain activity and enhanced memories of alcohol reward that may increase drinking or, during periods of abstinence or reduced drinking, lead to relapse. Alcohol-related stimuli known as cues may trigger the neuroadapted brain to crave alcohol.
While animal experiments suggest that craving is associated with certain brain regions (neuroanatomy) and neurotransmitters (neurochemistry), such models are limited by the animals' inability to report how they feel. In humans, craving is experienced differently at different stages of alcohol addiction and differently among drinkers at any single stage, complicating attempts to measure it accurately. To improve both measurement and understanding of the craving phenomenon, researchers are looking to new technologies such as the fMRI technique used in today's study.
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