Dr. Alan I. Leshner, Director of NIDA, described this research as extremely important, saying that, "Drug craving is a central aspect of addiction and poses a serious obstacle to treatment success for many individuals. Twenty years of neuroscience research have finally brought us to the point where we can actually see increases in activity in specific areas of the brain that are linked to the experience of craving. If we can understand the mechanisms by which certain stimuli cause craving in people addicted to cocaine or other drugs, more effective treatment strategies can be developed which target these areas of the brain."
People recovering from drug addiction are routinely advised to avoid friends and locations that have been previously associated with using drugs. When people addicted to cocaine or other drugs return to taking them after a period of abstinence, it is often because of an intense desire or craving for drugs actually caused by exposure to various stimuli in environments previously associated with drug use, whether or not the drugs themselves are now available.
In this study, researchers compared metabolic activity in various parts of the brain in a group of cocaine abusers (13 volunteers) and a group of controls (5 volunteers who had not used drugs other than nicotine and alcohol in the preceding 10 years). Test sessions consisted of presentations of cocaine-related stimuli and neutral stimuli. The cocaine-related stimuli consisted of drug paraphernalia, cocaine powder, and a videotape of people smoking and snorting cocaine; the neutral stimuli consisted of arts and crafts tools and a videotape of a person handling craft items.
In addition to measuring glucose metabolism in brain regions while the volunteers viewed the videos, the investigators used questionnaires for the volunteers to report their level of "urge" or "need" for cocaine. The cocaine-addicted group responded to the drug-related stimuli, but not to the neutral stimuli, with both drug craving and increased glucose metabolism in several regions of the brain. The control group showed no response to either set of stimuli. In addition, in the addicts, the increases in regional brain metabolism correlated significantly with the individuals' self-reports of craving: the more the craving the more brain activation.
The brain regions activated during exposure to the drug-related stimuli were the dorsolateral prefrontal cortex, amygdala, and cerebellum, regions involved in several aspects of memory and emotion. "Activation of these brain regions, which integrate emotional and cognitive aspects of memory, by drug-related cues, could contribute to one of the hallmarks of addiction, the excessive focus on activities that lead to further drug use," according to Dr. Edythe London of NIDA's intramural research program who initiated and directed the study.
Although the researchers did not directly test memory, Dr. Steven Grant, the lead investigator on the study said, "the findings suggest that the mechanisms of memory processing are as important to the understanding of cocaine craving as are the direct effects of the drug on the nervous system."
The study, carried out at NIDA's Intramural Research Program, is published in the October 15 issue of the Proceedings of the National Academy of Sciences. Funding for the study was also provided by the Counterdrug Technology Assessment Center of the Office of National Drug Control Policy.
NIDA, part of the National Institutes of Health, is the primary Federal agency conducting and supporting research to increase knowledge and promote effective strategies to deal with the health problems and issues associated with drug abuse and addiction. NIDA's intramural research program recently celebrated 60 years of conducting research on all aspects of drug abuse and applying that research to make drug abuse prevention and treatment more effective.
For more information about this study and other research supported by NIDA, contact the NIDA Press Office at (301) 443-6245. NIDA Media Advisories and other information is available on the NIDA Home Page at http://www.nida.nih.gov.