Tuesday, November 07, 2006

Where your brain sizes up your competition...

Goodman reports on a study led by Caroline Zink, a postdoctoral fellow at the National Institute of Mental Health, that found that several brain regions showed increased activity when people were evaluating their standings in a social hierarchy. Zink recruited 24 healthy volunteers — 12 men and 12 women — and had them play a game of skill while their brain activity was imaged using fMRI. Participants were told they would simultaneously be playing two other people: an inferior “one star” player and a superior “three star” player. These other players were invented, however, and their actions carried out by a computer. To convince the participants that the other players where real, the research team constructed elaborate ruses — postponing the start of the game for 15 minutes because another player was running late, for example, or leaving the room under the pretense of helping a player get set up. The volunteers were asked to press a button as soon as they were given a signal. If they responded quickly enough, they won a dollar. Though the researchers emphasized that the participants were not competing against the other players, they also made sure that the volunteers saw the scores of the one-star players and three-star players.

The results were clear and strong...When the volunteers won more money than the three-star players, raising their status in the game, the brain scanner showed increased activity in three brain regions: the anterior cingulate, an area that has been shown to monitor conflict and resolve discrepancies; the medial prefrontal cortex, which processes thoughts about other people; and the precuneus, a region that some speculate is involved in the brain’s ability to think about itself.

In contrast, when the one-star players won more money during the game than the volunteers, lowering their status, activity increased in the ventral striatum and the insular cortex, or insula. This area appears to be responsible for the somatic representation of emotional states, such as disgust. The ventral striatum is a deep brain structure linked in primates to motivation and reward, and may be part of the neural circuitry that keeps track of progress through learning.

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