Oh, so close. Just one more try.

It's hard to understand what keeps problem gamblers betting after a long losing streak. But a new study published May 5 in The Journal of Neuroscience suggests their brains' reward centers, part of the dopamine system (so-called because the neurons release the neurotransmitter dopamine), react the same way to a "near miss" as they would to a win.

Researchers from the University of Cambridge, U.K., used functional magnetic resonance imaging (fMRI) to scan the brains of 20 gamblers with varying degrees of gambling intensities while they played a computerized slot machine. The brain reward centers were active in problem gamblers even when the slot machine icons almost lined up but didn't. So the near miss delivered the dopamine, if not the dollars. 

"These findings are exciting because they suggest that near-misses may elicit a dopamine response in the more severe gamblers, despite the fact that no actual reward is delivered," said study co-author Luke Clark in a prepared statement. "If these bursts of dopamine are driving addictive behavior, this may help to explain why problem gamblers find it so difficult to quit."

Studies have linked the dopamine system with other forms of addiction, including drug abuse. "The results highlight some of the links between problem gambling and drug addiction, and have implications for both psychological and drug treatment for problem gamblers," Clark said.

Photo: iStockphoto/bonniej