Twin-peaks (the lateralized x-rhythms): a dual-EEG study of effective social coordination

Emmanuelle Tognoli

(w/ G.C. de Guzman, J. Lagarde, J.A.S. Kelso)

Human Brain and Behavior Laboratory – CCSBS – Florida Atlantic University



We investigated the behavioral and electrophysiological correlates of interpersonal motor coordination. The influence of other person’s concomitant motor activity was studied in pairs of subjects performing self-paced finger movements. Behaviorally, we explored the roles of subjects (leaders~follower) using directionality measures. Electrophysiologically, we aimed to identify the brain areas and their mechanisms correlated with asymmetrical social interaction and its effective (synchronized) coordination in the motor domain. We report two main results being specific of the states of effective social coordination: (1) a marked depression in the EEG power being maximal in the range 7.5-13 Hz, and peaking at two distinct occipital (alpha) and central (mu) locations and (2) a lateralized centro-parietal change in power associated to the pattern of motor coordination. These results support two conclusions. First, 'social attention', by way of a generalized desynchronization of the thalamo-cortical idling rhythms, is a prerequisite for effective social coordination. Second, subjects control the influence of other human on their own motor activity using the phi, a lateralized oscillatory system comprising two peaks appearing over centro-parietal areas. It is a gating mechanism of effective social coordination, "the customs officer telling the brain if the 'other' enters the 'self' or not". This newly described EEG rhythm seems to be of prime relevance for the emerging field of Social Neurophysiology and could be use to measure development of social interactions. [PPT]