Social interaction may cause monkeys’ brains to synchronize, according to a study published in Scientific Reports that measured two monkeys’ brain activity simultaneously for the first time.
Miguel Nicolelis and colleagues carried out simultaneous brain activity recordings on pairs of monkeys and found that their brain activity synchronized during a social interaction task. In the task, one monkey took the role of the ‘passenger’, and was carried in a robotic wheelchair, operated by a computer, to a food dispenser, while a second monkey, the ‘observer’, was watching. When the passenger reached the dispenser it was rewarded with a grape, while the observer monkey received a juice reward. The monkeys then swapped roles and their brain activity was once again recorded simultaneously while they performed the task.
The recordings indicated that the neurons from the motor cortex of the observing monkey responded in the same way as the neurons from the motor cortex of the monkey performing the task. The authors found that synchronized brain activity appeared to be dependent on factors such as the distance between the monkeys, how far away the food was from the wheelchair and the wheelchair speed. The authors suggest that the synchronization of the monkeys’ brains could be a key part of the neurological mechanism that enables primate social connectivity and social learning.
The authors caution that they only assessed how factors they controlled in the experiment, such as distances between monkeys, affect brain synchronization. Therefore, it is likely that other uncontrolled factors, such as head movements, eye contact and facial expressions could have contributed to the synchronization.