The Phi Complex as a neuromarker of human social coordination

May 16 2007

Researchers from Florida Atlantic University (FAU) have been able to identify neural signatures of effective, real-time coordination between people in one of the first studies in the field of social neuroscience to actually record, measure and analyze both behavior and brain activity simultaneously in two interacting humans.

Researchers used a specially designed dual-electroencephalogram (EEG) and the conceptual framework and methods of coordination dynamics in this study, “The Phi Complex as a Neuromarker of Human Social Coordination,” published in the May 8, 2007 Proceedings of the National Academy of Sciences . The research was conducted by Drs. Emmanuelle Tognoli, Julien Lagarde, Gonzalo DeGuzman and J.A. Scott Kelso in The Human Brain and Behavior Laboratory at the Center for Complex Systems and Brain Sciences in the Charles E. Schmidt College of Science at FAU.

Using EEG recordings, Tognoli and colleagues collected the brain activity of two people simultaneously performing continuous finger motion. At first, the two subjects were asked to wag their fingers but were not allowed to see each others' hands. Then, like the shutter release of a camera, the barrier placed between them was removed so they could see each other as they continued to wag their fingers. When 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 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.”

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.”

The success or failure of this information exchange revealed in this new brain rhythm will serve as a stimulus for the scientific community to further investigate the phi complex and its implications for understanding not only normal social cognition, but pathologies of social behavior.

“The ground-breaking research by Dr. Scott Kelso and colleagues leading to the discovery of this new brain rhythm related to human social interactions opens up the potential to now understand how and why we as humans relate to each other the way we do,” said Dr. Larry F. Lemanski, vice president for research at FAU. “Moreover, this exciting new finding may lead to a better understanding of and better diagnostic protocols for various neuropsychiatric disorders.”

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.”

This research has emerged as a result of continuous research support from the National Institutes of Mental Health (NIMH) over the course of more than 20 years for a project entitled, “Dynamic Patterns in Complex Biological Systems,” awarded to Kelso. This project was further enhanced by the Director's “Innovations” award, also from the NIMH awarded to Kelso and his team. The U.S. Office of Naval Research contributed funding in the later stages of the project and continues to support their ongoing research. The lead author of the paper, Tognoli, is an expert in cognitive neurophysiology and is a postdoctoral fellow in the Human Brain and Behavior Laboratory at FAU. Lagarde, an expert in motor neuroscience and a former postdoctoral fellow at the Center for three years, is now at the University of Montpellier in France. DeGuzman, a physicist by training, is currently a research associate professor at the Center.

Human Brain and Behavior Laboratory (HBBL) in the Center for Complex Systems and Brain Sciences at Florida Atlantic University

The human brain is a complex system possessing more than a trillion cells, many of which have more than a thousand connections. Out of this enormous complexity, patterns of cognition, emotion and behavior somehow emerge. What laws, principles and mechanisms make this possible? How does the human brain really work? What is its relation to what people do? What happens when the brain does not work, as in the many brain disorders that afflict our society? How do human brains work together? Using new concepts, strategies and methods for investigating complex systems and the latest technologies for imaging the human brain, a team of researchers in the laboratory is unraveling the secrets of how the human brain works and its relationship to mind and behavior. HBBL is led by Dr. J. A. Scott Kelso whose research has attracted more than $50 million in federal grants and significantly enhanced our understanding of the interplay of the mind and body.

Florida Atlantic University opened its doors in 1964 as the fifth public university in Florida. Today, the University serves more than 26,000 undergraduate and graduate students on seven campuses strategically located along 150 miles of Florida's southeastern coastline. Building on its rich tradition as a teaching university, with a world-class faculty, FAU hosts nine colleges: the Dorothy F. Schmidt College of Arts & Letters, the Charles E. Schmidt College of Biomedical Science, the Charles E. Schmidt College of Science, the Christine E. Lynn College of Nursing, the Harriet L. Wilkes Honors College, the Barry Kaye College of Business and the Colleges of Education, Engineering & Computer Science, and Architecture, Urban & Public Affairs.