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Release: June 25, 2001

Study links addiction, malfunction of brain's decision-making region

IOWA CITY, Iowa -- University of Iowa research results appear to confirm the hypothesis that drug addiction is, at least in part, a decision-making disorder. The study found that a large subset of substance-dependent individuals performed poorly on a clinical test designed to measure deficits in decision-making.

The clinical test, called the Iowa Gambling Task, was previously developed at the UI to assess decision-making impairment in patients with damage to a particular area of their brain known as the ventromedial prefrontal cortex. Earlier UI studies showed that this region of the brain controls aspects of decision-making. Other behaviors of substance-dependent individuals are also very similar to behaviors seen in patients with damaged ventromedial prefrontal cortices.

In the recent study, a UI team led by Antoine Bechara, Ph.D., UI assistant professor of neurology, used the Iowa Gambling Task to compare the decision-making ability of substance-dependent patients with that of normal control subjects and patients with damaged ventromedial prefrontal cortices. The study results appeared in the journal Neuropsychologia earlier this year.

As a group, the substance-dependent patients performed worse than the normal control subject on the gambling test, but not as poorly as ventromedial patients. However, within the substance-dependent group there was a wide range of performance, with three of five patients (61 percent) performing as poorly on the decision-making test as did patients with damaged ventromedial prefrontal regions.

"People have no problem with the concept of diseases of memory or attention," Bechara said. "But somehow it is not palatable to consider diseases of decision making. I think that decision-making disorders are an important component in some cases of addiction."

Most people try drugs, including alcohol and nicotine, at some point in their lives. However, only a small percentage become addicted such that they will continue to take the drug in spite of severe negative consequences. For Bechara, the critical question in addiction is why do people continue to choose to take drugs in the face of rising adverse consequences.

He suggests that while most people shy away from actions that have previously resulted in some form of punishment, either financial or social, addicts, like ventromedial patients, continue to choose courses of action that will likely result in an adverse outcome. In the face of immediate reward, these individuals appear to be insensitive to the likelihood of future punishment.

"A malfunction of the prefrontal cortex makes people exercise poor judgment in real life," Bechara explained. "So when they are exposed to something appealing, that poor judgment -- that disease -- disables their ability to exercise good judgment in controlling themselves."

The researchers looked at many characteristics of the study subjects in an attempt to find factors that might explain poor performance on the gambling test. Poor performance by any of the study's participants on the gambling test did not seem to be related to impaired cognitive abilities. Similarly, psychological problems, such as depression, anxiety and psychopathy, which often go hand in hand with addiction and which might influence addictive behavior did not correlate with poor performance on the gambling task.

Bechara noted that one factor that was strongly associated with a poor score on the gambling test was the inability to maintain employment, which also is one of the hallmarks of decision-making impairment in patients with damage to their ventromedial prefrontal cortex.

The study found that a formula that included duration of abstinence, years of abuse, times in treatment and maintaining gainful employment was the best predictor of whether a substance-dependent individual would perform poorly on the gambling test.

"We use these real-life behaviors of addicts in the formula, and we related it to the gambling test – our tool to measure decision making. And, sure enough, you find a relationship," Bechara said. "This group of substance-dependent individuals, who are like the prefrontal lobe patients, have a disease in their brain that affects their ability to make appropriate decisions. You could make the consequences as bad as possible and it still would not deter them."

The study suggests that the gambling test and similar tools could be useful in helping to identify people at risk of becoming addicts because of their impaired decision-making ability.

Bechara indicated that while the study found that impaired decision-making was a component of addiction for some substance-dependent individuals, addiction is a complex condition and there are many factors at work.

"We are trying to look at the entire neural circuitry that controls addiction," Bechara said.

Many current strategies aimed at tackling addiction are focused on blocking the action of brain pathways that are associated with reward from a drug or memory of that reward. However, Bechara argues that there is a fundamental problem with this approach.

"It is very difficult to specifically block only one effect of a pathway without disrupting other outcomes of the same pathway," Bechara said. "I think that our approach, which involves looking for ways to reinforce the self-control and decision-making function of the ventromedial prefrontal cortex, is a more promising strategy. You do not risk blocking a pathway that may also be critical to other important brain functions like memory and learning."

"Reinforcement of the ventromedial prefrontal cortex function may help self-control not only in the addiction process but also in other disorders that often co-exist with addiction," Bechara added.

The study was funded by the National Institute on Drug Abuse.

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