NIDA Study Offers New Clues About Connection Between Cocaine Abuse, Thinking, and Decision-making

New research shows that chronic cocaine abuse is clearly related to dysfunction in those parts of the brain involved in higher thought and decision-making. Scientists who performed the study suggest that the resulting cognitive deficits may help explain why those addicted persist in using the drug or return to it after a period of abstinence. The study 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 in Milwaukee.

"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. .

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 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 considerably 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 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."

Source: National Institute on Drug Abuse