Hard-wired. Blood flow to the ventral striatum (shown) is unusually low in compulsive gamblers, meaning they may have to win more than average people to feel the same reward.

Betting on the Brain

John is a Science contributing correspondent.

What drives compulsive gamblers to keep betting even after their lives fall apart? A new study suggests that their brains—like those of drug addicts—may be wired for addiction.

Compulsive gamblers and drug addicts describe similar cravings for their vices and experience a similar euphoria from them, but it has remained unclear whether gamblers exhibit the same kinds of brain abnormalities. For example, a typical feature of a drug addict's brain is an unusually weak activation of the ventral striatum, which provides the "reward" of pleasurable activities by boosting the signal molecule dopamine. It is thought that addicts get hooked on drugs in part because they do not receive the same level of satisfaction that average people get from daily activities. Another hallmark of severe drug addiction is a decrease in the activity of parts of the brain that inhibit impulsive behavior—a characteristic that leads to impaired judgment.

To test whether gamblers' brains have similar deficiencies, a team led by Christian Büchel, a neurologist at the University Medical Center Hamburg-Eppendorf, in Hamburg, Germany, used functional magnetic resonance imaging to compare the brains of 12 compulsive gamblers and 12 control subjects while they played a simple card game. The researchers presented each subject with two cards face-down. The players won 1 euro for overturning a red card and lost 1 euro for overturning a black card. Because the cards were randomly distributed, neither group won or lost significantly more often than the other. If compulsive gamblers have brains like the rest of us, Büchel expected the two groups to show similar patterns of brain activity.

But this was not the case. Reporting online 9 January in Nature Neuroscience, Büchel's team found the brains of compulsive gamblers were similar to those of drug addicts. When the gamblers chose a winning card, they exhibited significantly less blood flow to their ventral striatum than did the control group, suggesting they have to gamble more to get the same reward as non-gamblers. Like drug addicts, gamblers also showed decreased brain activity in parts of the brain that inhibit impulsive behavior.

The study is "credible and exciting," says Ray Dolan, a neurologist at the National Institutes of Health in Bethesda, Maryland. He notes, however, that it doesn't solve the puzzle of whether gamblers are born with abnormal brains or whether the gambling itself changes their brain activity.

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Posted in Brain & Behavior