Scientists believe they have discovered the neuronal basis in the brain for the “cornerstone of successful social interchange” – the ability to anticipate each other’s intentions or actions – after mapping the brain signals of male Rhesus monkeys during games that test social anticipation and cooperation.
The researchers say that understanding the nerve basis of cooperative social interactions “paves the way for the targeted treatment of social behavioral disorders such as autism spectrum disorders.”
Dr. Keren Haroush – lead author of the study published in the journal Cell – explains: “Many conflicts or adversarial interactions arise from an inability to accurately read another’s intentions or hidden state of mind.”
“Therefore,” adds Dr. Haroush, a postdoctoral fellow at the Massachusetts General Hospital-Harvard Medical School Center for Nervous System Repair, “understanding where and how these computations are performed within the brain may help us better understand how such complex social interactions occur.”
The researchers conducted numerous trials of Rhesus monkeys confronted with the classic prisoners’ dilemma game.prisoners’ dilemma game, and conducted numerous trials of the task. The authors say:
“The key to succeeding in the game relies on one’s ability to anticipate the other’s concurrent, yet-unknown intentions.”
The game task incorporated two crucial properties for the monkeys, the authors explain. “One is that the outcome is contingent upon the mutual concurrent decisions of both individuals, and therefore no one decision guarantees an individual’s outcome, and the other is that both decisions can be either concordant or discordant.”
A monkey received the largest juice reward when it decided to defect while the opponent chose to cooperate, whereas both monkeys received a lower reward for mutual cooperation – and the lowest reward for mutual defection.
The researchers recorded signals from the anterior cingulate, “which is involved in learning social information and is connected with other brain regions that play a role in interactive behavior.”
The results unfolded in the following way:
- The monkey’s own decision on a given trial was reflected by the activity of about a quarter of the anterior cingulate neurons
- But when it came to the opponent’s yet-unknown upcoming choice, this affected the activity of about a third of neurons.
“Remarkably,” the authors conclude, “other-predictive cells during joint interactions constituted over a third of the cingulate task-responsive population and were more prevalent than cells encoding the monkey’s own present selections.”
Activity in the dorsal anterior cingulate cortex accurately predicted the monkey’s own choices in 66% of the trials, and the opponent’s yet unknown choices in 79% of the trials.
When the researchers used electrical stimulation to disrupt the activity of the neurons at the back of the anterior cingulate cortex, the monkey was less likely to be cooperative after the opponent had shown cooperation in a trial.
This finding, the authors say, suggests that these neurons “play a critical role in incorporating recent positive interactions to make mutually beneficial decisions.”
The researchers will continue to investigate how the brain encodes complex interactions, with the hope of developing new treatments for social behavioral disorders.
Senior author Dr. Ziv Williams, a neurosurgeon at Massachusetts General Hospital, explains: “The electrical stimulation technique we used is very similar to what is currently used with deep-brain stimulation for treating disorders such as depression and obsessive-compulsive disorder.
“This study may therefore help guide the future treatment of medically intractable disorders such as autism and antisocial personality disorder, which are often characterized by difficulty with social interactions.”
The authors have published a “video abstract” of their study at YouTube:
Other recent research has brought clues on the neuronal basis of disorders such as autism. For example, in January a study identified a part of brain key to controlling attention.
Earlier this month, pediatric neuroscientists published research suggesting that abandoned children are at risk of social communication difficulties and autism.