NIDA Study Offers New Clues About Connection Between Cocaine Abuse, Thinking, and Decision-making
New research, funded in part by the National Institute on Drug
Abuse (NIDA), National Institutes of Health, shows that chronic
cocaine abuse is directly related to dysfunction in areas of the
brain involved in higher thought and decision-making. The scientists
who performed the study suggest that the resulting cognitive deficits
may help explain why abusers persist in using the drug or return
to it after a period of abstinence. The study, published in the
December 8, 2004 issue of the Journal of Neuroscience, was conducted
by Dr. Robert Hester of Trinity College in Dublin, Ireland, and
Dr. Hugh Garavan of Trinity College and the Medical College of Wisconsin
"Addictive substances such as cocaine can damage the dopamine
system in the brain, and there is a high concentration of dopamine
receptors in brain regions involved in higher-order decision-making
processes," says NIDA Director Dr. Nora D. Volkow. "By
employing functional neuroimaging to examine the neural changes
that often result from chronic cocaine abuse, these scientists have
identified another aspect of cocaine's effect on the brain that
may help explain why individuals persist in these behaviors despite
the negative consequences."
In the study, the scientists enlisted 15 active cocaine abusers
and 15 healthy individuals who have never used the drug. Each participant
completed a task in which they viewed memory lists of letters for
6 seconds and "rehearsed" each list for 8 seconds. The
participant then pressed a button when they were presented with
a letter that was not part of the preceding "memorized"
list. During the task, the participants' brains were analyzed via
functional magnetic resonance imaging (fMRI), a noninvasive imaging
technique that illustrates nerve cell activity during the performance
of a specific task.
Results showed that the cocaine abusers were significantly less
proficient than the controls at accurately completing the task.
The scientists found that the demands of working memory required
increased activation of two brain regions, the anterior cingulate
cortex (ACC) and the prefrontal cortex. These areas, which have
been consistently associated with memory and higher brain function,
are richly interconnected and have bidirectional communication with
other regions associated with cognition.
"Previous research that examined cognitive function in cocaine
abusers identified decreased activity in the ACC," says Dr.
Garavan. "But our study is the first to show that the difficulty
cocaine users have with inhibiting their actions, particularly when
high levels of reasoning and decision-making are required, relate
directly to this reduced capacity for controlling activity in the
ACC and prefrontal regions of the brain."
The National Institute on Drug Abuse is a component of the National
Institutes of Health, U.S. Department of Health and Human Services.
NIDA supports more than 85 percent of the world's research on the
health aspects of drug abuse and addiction. The Institute carries
out a large variety of programs to ensure the rapid dissemination
of research information and its implementation in policy and practice.
Fact sheets on the health effects of drugs of abuse and information
on NIDA research and other activities can be found on the NIDA home
page at http://www.drugabuse.gov.