Previous studies have shown that when a monkey watches his or her fellow monkey perform a task – grabbing a tasty morsel, for example – a similar set of neurons in the observer’s brain’s motor cortex start firing. It’s as if they are also reaching for the piece of food.
Now new research, published in the journal Scientific Reports, has found that this synchronizing behavior is affected by several social factors, including social hierarchy, food competition, and how close the observer is to the other animal.
Unlike studies that have been done in the past, which recorded the brain activity of monkeys one at a time, researchers from Duke University developed a multi-channel wireless system that allowed them to monitor the brain activity of two adult macaques concurrently. The team observed high levels of synchronization in the brain between pairs of monkeys during social interactions – a process referred to as interbrain cortical synchronization.
“We believe our study has the potential to open a complete new field of investigation in modern neuroscience by demonstrating that even the simplest functions of the motor cortex, such as creating body movements, are heavily influenced by the type of social relationships among the animals participating,” senior author Miguel Nicolelis explained in a statement.
One task measured the brain activity of two macaques as one was transported in a pre-programmed wheelchair to a food dispenser on the other side of the room while the other watched. When the wheelchair-bound monkey reached his or her destination, they were rewarded with a fresh grape. At the same time, the observer was given fruit juice so that, in a sense, the pair were interacting socially.
The results show neurons in the motor cortices of the brain of the observer lighting up, mirroring those of the passenger. A similar set of so-called mirror neurons, though little understood, may be key to how humans relate to one another in social situations. Some neuroscientists suggest a lack of these neurons could play a role in conditions affecting social skills, like autism.
Interestingly, the level of brain activity revealed how close the observer monkey was to the passenger monkey, peaking at roughly 1 meter (around 3 feet) – but only if the observer monkey was of a lower rank than the passenger monkey. When the animals' social statuses were reversed, levels of brain activity in the observer monkey remained fairly consistent.
The next stage is to apply a similar technique to humans. Nicolelis has already announced plans to begin trials on brain synchrony in humans using electrode caps and a functional MRI.
“Using a non-invasive version of this approach, we may be able to quantify how well professional athletes, musicians or dancers are working together, or if an audience is engaged in what they’re seeing, listening or imagining,” he added.