New research shows that parts of the brain involved in monitoring behaviors and emotions show different levels of activity between cocaine users and non-drug users. The differences remained even when both groups performed equally well on a psychological test. These impairments suggest that treatments aimed at improving these functions could help treat addiction.

Although there have been many studies that have found decreased brain activity in drug-addicted individuals, it’s never before been clear if the differences were due to varying levels of interest or ability between drug addicts and healthy control subjects. “This is the first study to look at two groups matched for performance and interest—and we still see dramatic differences in the brain regions that play a very significant role in the ability to monitor behavior and regulate emotion, which are both important to resisting drug use,” said Rita Goldstein, lead author of the study and a psychologist at the US Department of Energy’s Brookhaven National Laboratory.

The researchers studied 17 active cocaine users and 17 demographically matched healthy control subjects; both groups were asked to push one of four colored buttons corresponding to the color of type used to present words that were related to drug use (“crack” and “addict”) or neutral household items. Subjects were intermittently given monetary rewards for fast, accurate performance for a maximum of $75.

Both groups performed equally well on the same test while lying in a MRI scanner, and their performance improved when they knew they would be earning the highest monetary reward. During the test, scientists used functional MRI to measure the amount of oxygen being used by specific regions of a brain to monitor brain activity.

It was found that cocaine users had reduced activity in a portion of the brain that usually becomes more active when monitoring behavior. Activity was lowest when there was no monetary reward and when the words shown were neutral items. Among the cocaine users, activity levels were lowest in those who had used cocaine most frequently in the 30 days prior to the test.

Cocaine users also had reduced activity in a part of the brain that usually becomes less active when someone is successfully suppressing emotions. Activity rewarded by money was lowest in the people who were most successful in suppressing the task-induced craving. In non-drug users who did not report craving, activation in this region was normal.

In the healthy subjects, the functions within the behavior-monitoring and emotion-monitoring regions were interconnected, but they were disconnected in the cocaine users. “When you really have to suppress a powerful negative emotion, like sadness, anxiety, or drug craving, activity in this brain region is supposed to decrease, possibly to tune out the background ‘noise’ of these emotions so you can focus on the task at hand,” Goldstein said.

"Our results show that activity in this region indeed went down in the drug-using group, suggesting they were actively trying to suppress craving. Indeed, subjects who reported the highest levels of task-induced craving were the least able to suppress activity in this particular brain region. This could be because these drug users were still being distracted by background 'noise' stimuli, like memories of having taken drugs or anticipation of further use," Goldstein continued.

This gives scientists some clues as to what happens when drug users are able to suppress cravings and how that might work with a decreased ability to monitor behavior to make some people more vulnerable to drug addition. The study also shows that it is important to improve activity in the behavior-monitoring brain region, possibly by using pharmacological and behavioral approaches to increase motivation. Treatments aimed at improving activity in the emotion-monitoring region may further help people regain self-control, especially during craving.