Now, Paul Glimcher and colleague Michael Dorris have used a game-playing approach to demonstrate that a region of the cortex called the lateral intraparietal (LIP) area is active when monkeys are making subjective internal decisions about the desirability of an action--in this case, moving their eyes to a target. According to the researchers, their findings represents a step toward understanding the machinery by which the brain processes decisions.

In their studies, the researchers first tested the behavior of humans competing in a game in which a player was asked to click on a computer mouse to choose one of two buttons to receive either a certain monetary reward or a risky choice that could yield a larger reward. An opponent, meanwhile, was asked to select an option that would prevent the reward, and the researchers could vary the cost to the opponent of making that selection.

The basic aim of the researchers was to create a situation in which there was no single correct choice, so that subjects adopted a mixed strategy, reflecting that the subjective desirability of the choices was equal.

Once the researchers determined that the humans playing the game adopted just such a strategy, they then developed a computer "opponent"--a program designed to elicit the same mixed strategy. They tested the computer program against human players, determining that it elicited the same mixed strategy.

They then trained monkeys to play a version of the game against the computer, in which the animals were required to choose to glance at specific colored targets to receive sips of water. The computer program would analyze their responses and vary the parameters to elicit the same strategy. The researchers determine
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Contact: Heidi Hardman
hhardman@cell.com
617-397-2879
Cell Press
13-Oct-2004