( esearchers made the average payoff for ...)Gambling monkeys give insight into neural machinery of risk

esearchers made the average payoff for the risky target less than for the safe target, "we found that they still preferred the risky target," said Platt. "Basically these monkeys really liked to gamble. There was something intrinsically rewarding about choosing a target that offered a variable juice reward, as if the variability in rewards that they experienced was in itself rewarding."

Even when the researchers subjected the monkeys to a string of "losses," the high of a "win" appeared to keep them going, said Platt.

"If they got a big reward one time on the risky choice, but then continued to get small rewards, they would keep going back as if they were searching or waiting or hoping to get that big payoff. It seemed very, very similar to the experience of people who are compulsive gamblers. While it's always dangerous to anthropomorphize, it seemed as if these monkeys got a high out of getting a big reward that obliterated any memory of all the losses that they would experience following that big reward," said Platt.

Confident that they had developed a valid animal model that would reveal insights into the brain mechanism for assessing risk, the researchers next explored the neural circuitry that governed that assessment. They threaded hair-thin microelectrodes into a brain region called the posterior cingulate cortex, which studies in humans and animals had implicated in the processing of information on rewards. They then measured the electrical activity of neurons in the region as they administered the same behavioral task to the monkeys.

"We found that the neurons behaved very similarly to the monkeys," said Platt. "That is, as we increased the riskiness of a target, the neurons' activity would go up in the same way the monkey's frequency of choosing that target would go up. It was amazing the degree to which the activity of these neurons paralleled the behavior of the monkeys. They looked like they were signaling, in fact, t
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Source:Duke University Medical Center

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