Nature Neuroscience pp 1220 - 1227

Making the right choices in the face of uncertain outcomes is a critical skill in life, but to do that, the brain must have a way to evaluate the risks. Neurons in a part of the brain called the posterior cingulate cortex represent the riskiness of choices in monkeys, reports a paper in the September issue of Nature Neuroscience.

Faced with a choice between a reward that was guaranteed and an uncertain reward (a 50:50 chance of a reward that was smaller or larger than the guaranteed one), monkeys in this study typically chose to gamble. Indeed, the more risky the experimenters made the reward, the more likely the monkeys were to choose it, even when the probability of obtaining a larger reward from the risky target was reduced so that the risky choice led to a smaller average reward. During the task, the authors recorded from neurons in the posterior cingulate cortex, and found that many of them responded more strongly to riskier targets. The authors suggest that these neurons may represent the subjective value of the choice to the monkey, rather than the absolute value of the reward.

Nature Neuroscience pp 1255 - 1262

A brain region called the medial orbitofrontal cortex mediates the influence of emotions like regret on decision-making, shows a functional imaging study in the September issue of Nature Neuroscience.

People offered a certain $50 or a 1 in 100 chance of winning $5000 will usually choose the sure thing. But people are more likely to take the risky alternative if they know they�ll find out later whether they would have won the gamble. Economists attribute this behavior to a desire to avoid the regret that would result from knowing that one has passed up a big prize.

Subjects in the study were offered a choice of two gambles, one riskier than the other, and the authors induced regret on some trials by providing outcome information for both gambles. As the experiment proceeded, subjects modified their choices to reduce the potential for regret, and activity in the medial orbitofrontal cortex and amygdala increased. This pattern of brain activity was seen after a choice that inspired regret (when the riskier gamble that was not chosen paid off), and when the subjects were deciding which gamble to choose. This pattern of activity was absent when subjects' 'choices' were determined by a computer - indicating that personal responsibility was important for activating these areas.

Previous work has shown that patients with lesions to the orbitofrontal cortex have difficulty making appropriate choices in such gambling tasks, lending support to the authors' conclusions.