Scientists identify brain's 'trust machinery'

Washington, May 22 : Researchers at the University of Zurich claim that they have found the 'trust machinery' of the brain.

The boffins have identified brain centres triggered by betrayal of trust, which could be suppressed by brain chemical oxytocin thus helping people learn to trust again.

They believe that the findings would not only offer insights into neural machinery underlying trust, it could also help in understanding the neural basis of social disorders such as phobias and autism.

The team led by Thomas Baumgartner asked the participants to play two types of games-a trust game and a risk game.

In the trust game, subjects were asked to contribute money, with the understanding that a human trustee would invest the money and decide whether to return the profits, or betray the subjects' trust and keep all the money.

In the risk game, the subjects were told that a computer would randomly decide whether their money would be repaid or not.

They were also given doses of either the brain chemical oxytocin (OT) or a placebo via nasal spray.

Previous studies have shown that oxytocin increases people's willingness to trust others.

During the games, the subjects' brains were scanned using functional magnetic resonance imaging using harmless magnetic fields and radio waves to map blood flow in brain regions, which reflects brain activity.

The study showed that oxytocin affected the subjects' responses specifically related to trust.

The findings revealed that in trust game, OT decreased activity in two brain regions the amygdala, which processes fear, danger and possibly risk of social betrayal and an area of the striatum, part of the circuitry that guides and adjusts future behaviour based on reward feedback.

"If subjects face the non-social risks in the risk game, OT does not affect their behavioural responses to the feedback. Both subjects in the OT group and the placebo group do not change their willingness to take risks after the feedback," said the researchers.

"In contrast, if subjects face social risks, such as in the trust game, those who received placebo respond to the feedback with a decrease in trusting behaviour while subjects with OT demonstrate no change in their trusting behaviour although they were informed that their interaction partners did not honour their trust in roughly 50 pct of the cases," they added.

The study appears in the May 22, 2008, issue of the journal Neuron, published by Cell Press.

ANI