Researchers at Florida Atlantic University (FAU) have identified neural signatures of real-time coordination between people. In one of the first studies in the field of social neuroscience, they actually recorded, measured and analyzed behavior and brain activity simultaneously in two interacting humans.

The researchers used a specially designed dual-electroencephalogram (EEG) while applying concepts and methods of coordination dynamics in the study, published in the Proceedings of the National Academy of Sciences. Employing EEG recordings, Dr. Emmanuelle Tognoli and colleagues collected the brain activity of two people simultaneously performing continuous finger motions.


Two subjects were first asked to wag their fingers, but were not allowed to see each others' hands. Then, the barrier placed between them was removed so they could see each other as they continued to wag fingers. When the subjects were allowed to see each others' fingers moving, sometimes they adjusted their own movements and synchronized with each other, and sometimes they did not, behaving independently.

“While many interactions between people rely on mutual information exchange, little is known about how such social processes are integrated in the brain,"

said Dr. Kelso, the Glenwood and Martha Creech Eminent Scholar in Science and founder of the Center for Complex Systems and Brain Sciences.

“What this research suggests is that a unique pattern can be seen in the brains of two people interacting and that these brain activities distinguish independence from cooperation. This new brain rhythm that we have discovered and termed the ‘phi complex’ actually distinguishes when you’re socially interacting and when you’re not."

The Phi Wave Complex

Phi is one of a number of brain rhythms that exist in the awake human brain and appears to have a social function. Rhythms or oscillations are the natural language of the brain. They are the signature of the underlying cortical networks and are characterized by their frequency, strength and location.

“Phi” operates in the 10 Hz band (10 oscillations per second) and is located above the right centro-parietal cortex. It consists of two components: one favors independent behavior and the other favors interpersonal coordination between people.

“The phi complex is closely tied to the success of the mutual interaction between people and is not merely a consequence of one person imitating the other,” said Tognoli. “Our measure of behavior, the phase or timing relationship between the actions of two people, is important because it characterizes the informational exchange between their brains."

Autism and Schizophrenia Marker

The phi complex may prove to be a sensitive probe or neuromarker of neuropsychiatric disorders such as autism and schizophrenia where the inability to have harmonious social interactions is problematic. In addition, this research opens up many new and untapped possibilities to identify the neural mechanisms of real-time social behavior between humans such as leader- follower, male-female and enemy-friend relationships.

“An ever increasing number of mathematicians, physicists and computer scientists in collaboration with neuroscientists are trying to understand how patterns are generated in the human brain and their relation to behavior,” said Dr. Gary Perry, dean of the Charles E. Schmidt College of Science.

“This cross-disciplinary interaction at the cutting edge of science has proven very fruitful, and Dr. Kelso and his team are pioneers in this area.”

Image: Loial Otter/flickr

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