THURSDAY, April 19 (HealthScout) -- The more you surprise your brain, the better it likes it. And that discovery could lead to better treatment for addictions, a new study says.

Until recently, scientists thought that the neural pathways that connect to the brain's pleasure centers responded to what people like, says P. Read Montague, associate professor of neuroscience. He is the director of Baylor College of Medicine's Center for Theoretical Neuroscience and study senior author.

But, when that theory was tested on 30 people -- by squirting water and fruit juice at them, in both an expected and random sequence -- researchers found the brain's reward pathways responded much more strongly to the unexpectedness of the stimuli, rather than their pleasurable effects, says Montague.

Montague and Dr. Gregory Bern of Emory University's Functional Neuroimaging Group used magnetic resonance imaging (MRI) to record pictures of the brain activity as the liquids were squirted into the participants'mouths.

The nucleus accumbens, often identified as the brain's pleasure center, measured a much stronger response when the juice or water squirt was unexpected.

After the MRIs the participants were asked whether they preferred juice or water. "The surprising thing," says Montague, is "when we gave them their preferred juice or water, it [the brain] didn't light up at all, " but rather, reacted to the unexpectedness of the event.

"These processes are not conscious. They are not as clearly related to what we think of as reward," says Montague. And, this finding may help in treat addictions, he says, by clarifying the brain pathways involved in cocaine or heroin dependence.

"The whole way addiction is conceptualized," says Montague, "is that it's rational willful power," that addiction is a brain disease. But, "just changing the predictability of the stimulus causes an activation in the reward pathways and the nucleus accumbens that rivals what you get when you inject cocaine."

At least one part of treating addiction, says Montague, "is understanding these processes are unconscious and work before you can get a hold of them. The strength of the response is so clearly related to predictability, that's the avenue to pursue."

Regina Carelli, assistant professor of psychology at the University of North Carolina in Chapel Hill says the findings are very interesting. "We know [certain areas of the brain] encode information about food, water and cocaine. But to see they're encoding predictability over preference is somewhat surprising."

But, she adds, although this study is intriguing, Montague was not testing reactions to addictive substances, and future studies would be needed to make the link from fruit juice to cocaine.

The study is published in the April 15 issue of Journal of Neuroscience

What To Do

This study is in its very earliest stages; any practical effect on treating addiction still may be years away.

Learn more about the brain by flipping through the pages of the Whole Brain Atlas.

Find out more about magnetic resonance imaging on How Stuff Works.

For more HealthScout stories on the pleasure centers of the brain, click here.