Brain's fear centre also evokes kindness

A small structure in the brain associated with evoking fear till date has now been found to be influencing positive social functions like kindness and what might be called charitable giving in humans.

The amygdala, a small structure at the front end of the brain's temporal lobe, has long been associated with negative behaviour generally and specifically with fear.

Michael Platt, professor in the University of Pennsylvania, along with Steve Chang from Yale University and collaborators from Duke, showed that amygdala can also evoke kindness.

Such a link could have implications for people with autism, schizophrenia or anxiety-related disorders.

"What we're trying to do is both identify and understand the basic brain mechanism that allows us to be kind to each other and to respond to the experiences of other individuals," Platt added.

To make this discovery about the amygdala, Platt and his team looked at the social behaviour of rhesus macaques.

The researchers incorporated a task they developed four years ago as a way to observe how animals make beneficial decisions.

Simultaneous to watching the monkeys' behaviour, Platt and his colleagues recorded the neural activity of the amygdala of each animal.

They found that neural activity in the amygdala reflected the value of the recipient's reward in the same way it reflected the value of the reward for the actor.

When the bonding hormone oxytocin was introduced, behaviours changed rapidly.

"When people inhale oxytocin, there is a change in blood flow to the amygdala, which we think might be involved in making people kinder and more receptive to others," Platt noted.

In his experiment, the monkeys receiving oxytocin became more willing to give to other monkeys and paid more attention to them after offering the rewards.

Rhesus macaques offer a valuable comparison to humans because the animals model many of the social behaviours in which humans engage.

They also live in large social groups and form what Platt described as long term social bonds.

The findings were published in the journal Proceedings of the National Academy of Sciences.