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If you want to make someone really happy, bring her a present when she least expects it, new research suggests.
Human brain
gets a kick out
of surprises
Finding may offer
clues to drug addiction
By Julia Sommerfeld
    April 15 —  New research offers a biological explanation for why toddlers are so enthralled by the game jack-in-the-box and we all get a kick out of surprise parties. Brain scans show humans are hard-wired to derive pleasure from such unexpected events.  

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       SCIENTISTS USING magnetic resonance imaging (MRI) to measure brain activity in response to pleasurable stimuli found that the nucleus accumbens — a region known as the brain’s pleasure center — responded much more strongly when the event was unanticipated.
       “What this means is that the part of the brain that has always been associated with pure pleasure really cares about when you get something unexpected,” said lead author Dr. Gregory Berns, an assistant professor of psychiatry at Emory University in Atlanta. “So if you get a present for your birthday, that’s nice. But you’ll like it a lot more if you get a present and it’s not your birthday.”
       Because the same region of the brain is activated by cocaine and other drugs, the study may yield new insights on addiction, the researchers said.
       Twenty-five adult volunteers underwent MRI scans while having fruit juice or water squirted into their mouths through a tube either in a predictable or unpredictable pattern. During the predictable run, water and juice alternated at fixed interval of 10 seconds; during the unpredictable run, the order and interval were randomized. The subjects were then asked which drink they preferred.
       The scans revealed that the brain’s pleasure center was most strongly activated when the squirts were unpredictable. This held true regardless of whether the subjects preferred juice or water.
A graphic illustrates how the nucleus accumbens -- the area in the middle of the axis -- is activated in response to an unpredictable event.
       Activation in this area of the brain suggests a rush of dopamine — the brain’s feel-good neurotransmitter, the researchers said.
       “The region lights up like a Christmas tree on the MRI,” said study co-author Dr. P. Read Montague, an associate professor of neuroscience at Baylor College of Medicine in Houston. “That suggests people are designed to crave the unexpected.”
       The findings were published Sunday in the Journal of Neuroscience.
       The researchers did not examine how the brain would react to bad surprises, but Berns said that negative stimuli are processed in a different area of the brain. He speculated that unpredictability would probably amplify the aversiveness of negative events just as it enhances the pleasure of pleasant events.
       Berns explained the significance of unpredictability from an evolutionary point of view: “The brain is tuned to pick up change. It’s linked to survival. When something surprising happens in the environment, that can be life or death.”
Street drugs - the toll on the body <interactive>

       The scans also revealed that unpredictable events activate the brain in a manner similar to cocaine, according to Montague.
       This discovery — that surprising someone with natural, healthy stimuli like juice or water can activate the brain’s reward center to the same degree as cocaine and other drugs — could help researchers better understand the biological basis of drug addiction, Montague and Berns said.
       “We know people take drugs because they like what it’s doing to their brains. But what this study suggests is that what they like is the unusual nature of the drug experience,” said Dr. Alan Leshner, director of the National Institute on Drug Abuse, which helped fund the research.

       Dr. George Koob, a professor of neuropharmacology at Scripps Research Institute in La Jolla, Calif., put forth a similar explanation.
       “Cocaine and other psychostimulants make stimuli that are rewarding even more so,” he said, “and in a sense make it like a surprise.”
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