This is your brain on 'risk-taking'

A new study has shed light on what's going on inside our heads as we decide whether or not a bird in the hand is worth two in the bush.

Researchers at Washington University School of Medicine in St. Louis located a region of the brain involved in decisions made under conditions of uncertainty, and identified some of the cells involved in the decision-making process.

The work could lead to treatments for psychological and psychiatric disorders that involve misjudging risk, such as problem gambling and anxiety disorders.

"We know from human imaging studies that certain parts of the brain are more or less active in risk-seeking people, but the neural circuits involved are largely unknown," said senior author Ilya Monosov. "We found a population of value-coding neurons that are specifically suppressed when animals make a risky choice."

Value-coding neurons are cells whose activity reflects the value of a stimulus - in this study, the more juice that was offered to a monkey, the bigger the neurons' response. However, shortly before the subject made a risky choice, these neurons became suppressed.

The researchers also found a separate group of neurons that signal information about uncertainty after the choice but before the risky outcome.

To study the neuronal circuits of risk taking, Monosov and colleagues gave rhesus monkeys - whose brains are structured very similarly to ours - a choice between a small amount of juice or a 50-50 chance of receiving either double that amount of juice or nothing at all. Over time, the amount of juice received under either condition would be the same, but one option was safe and the other risky.

It turns out rhesus monkeys like to live on the edge. The monkeys chose the risky option more often than the safe option. Moreover, the researchers found that a group of value-coding neurons in a part of the brain called the ventral pallidum were selectively suppressed when monkeys chose a risky option over a safe one. The ventral pallidum plays an important role in controlling levels of dopamine - a molecule that transmits signals between neurons and makes us feel good.

"There are no anatomically targeted treatments for psychiatric disorders associated with misjudging risk, such as pathological gambling and anxiety," Monosov said. "Now that we know where uncertainty is processed in the brain, we can start looking for ways to modulate it."

The study appears in Journal of Neuroscience.