The phi complex: a neural signature for effective social coordination and its breakdown


Tognoli, DeGuzman, Lagarde & Kelso


Using the concepts, tools and methods of coordination dynamics, we seek to identify  neural signatures of effective interpersonal coordination and its breakdown. We recorded the dual-EEG of 8 pairs of subjects, while they performed continuous self-paced finger movements. Each trial (n=36) included three successive phases lasting 20 seconds: vision of each others disabled, then enabled, then disabled again. The behavioral coupling (phase-locked movements) was monitored continuously to identify periods of effective coordination. Using high-resolution spectral analysis of the subjects’ dual-EEG before and during visually mediated social coordination, we identified a pair of oscillatory components (f1, f2), appearing above right centroparietal areas. The dynamics of this phi complex was able to dissociate effective social coordination from its breakdown: Increase of the first component favored unsynchronized interpersonal behaviors while increase of the second component favored synchronized ones. We show unambiguously that this EEG rhythm is spectrally, spatially and functionally distinct from the rolandic mu. Our results indicate that rolandic mu is not specific to coordination behaviors and that the lateralized centro-parietal phi complex is. They further suggest that subjects use this phi mechanism to gate the influence of other human beings on their own actions. [PPT].