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news.Neurobiologists have successfully used monkey models to pinpoint circuitry in the brain that assesses the level of risk in a given action. The work is said to have provided insight into risky behaviors engaged in by humans.
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The findings gained from experiments in which monkeys were given a chance to gamble to receive juice rewards, could give insights into why humans compulsively engage in risky behaviors, including gambling, unsafe sex, drug use and overeating.
In their experiments, the researchers gave two male rhesus macaque monkeys chances to choose to look at either of two target lights on a screen. Looking at the “safe” target light yielded the same fruit juice reward each time. However, looking at the “risky” target light might yield a larger or smaller juice reward. The average juice reward delivered by looking at either target was the same.
The monkeys overwhelmingly preferred to gamble by looking at the risky target. This preference held, regardless of whether the scientists made the risky target reward more variable, or whether the monkeys had received more or less fruit juice during the course of the day. Even when the researchers subjected the monkeys to a string of “losses,” the high of a “win” appeared to keep them going.
The researchers next explored the neural circuitry that governed that assessment by threading hair-thin microelectrodes into a brain region called the posterior cingulate cortex, 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.
Analysis of the neuronal activity indicated that the neurons were reflecting the risk value the monkeys placed on the target, rather than an after-the-fact response to the payoff. When the risks were high greater neural activity was observed. While the researchers believed they have isolated one component of the neural machinery of risk, they do not believe they have mapped the entire circuitry.
The studies with monkeys can guide studies in mice, in which scientists can make genetic alterations in the mice and study the behavioral effects of those alterations. Such studies could contribute to understanding of the genetic basis of compulsive behaviors and other such behavioral disorders.