The amygdala, the small, almond-shaped structure located at the front end of the brain's temporal lobe, has long been associated with negative, primal behaviors such as fear and rage. However, new research from scientists at the University of Pennsylvania discovered that this unique collection of nuclei can also play a role in positive social behaviors such as kindness and charity. These findings could help researchers better understand disorders such as autism, schizophrenia and anxiety.
"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," said Michael Platt, co-author of the study, in a press release. "We're also trying to use that knowledge to evaluate potential therapies that could improve the function of these neural circuits, especially for those who have difficulty connecting with others."
In order to make the discovery, Platt and his team examined the social behavior of rhesus macaques, a species of non-human primates that he has studied for 22 years, as they put them through a reward-donation task that allowed them to observe how they make beneficial decisions.
"We have an actor monkey and a recipient monkey," he said. "The actor monkey learns that different colored shapes on the screen are associated with a reward that can be delivered to himself, to the monkey next to him, to both or to nobody at all. They learn that over a couple of weeks."
The researchers then present the actor monkey with a set of choices and potential rewards — they have the ability to keep the reward, share it or give it away.
"Generally, our actor monkeys prefer to reward the other monkey rather than let it go unclaimed," said Platt. "They are more likely to give to those they're more familiar with, and also to monkeys subordinate to them. The social relationships shape how prosocial the actor monkeys are."
While the monkeys conducted these behaviors and tasks, Platt and his team recorded the neural activity of the amygdala and found that it correlated with the value of the reward for the actor, allowing them to predict when the actors would give rewards based on the neural activity of this structure.
The results were published in the Dec. 14 issue of the Proceedings of the National Academy of Sciences.
