Two-in-one: inter-brain hyperconnectivity during cooperation by simultaneous EEG-fNIRS recording

Hyperscanning is a quite recent paradigm in neuroscience which consists in the\r\nsimultaneous recording of the cerebral activity of two or more subjects involved in\r\ninteractive tasks. This measure allows to explore inter-personal brain mechanisms\r\nunderlying and generated by social interactions, when participants are continuously\r\nmodifying their own actions according to the partner’s ones. Previous studies showed\r\nthat this mutual adaptation results in interactional brain synchrony to which all\r\nmembers contribute; accordingly, these mechanisms are involved only during interactive\r\nsocial relations and cannot be captured by conventional single-subject recordings.\r\nHowever, hyperscanning research recurred to either electrocortical or imaging\r\ntechniques to explore the temporal dynamics or the brain networks involved in interactive\r\nbehaviors but, to our knowledge, there are no previous attempts to acquire\r\nboth measures jointly. Thus, the aim of the present study was to investigate the cognitive\r\nprocesses underlying the execution of joint cooperative actions performed by\r\ncouples of subjects by means of a multi-method hyperscanning technique. We aimed\r\nat assessing to what extent cortical synchronization, in both electrophysiological\r\n(by EEG) and hemodynamic (by fNIRS) components, could emerge between two\r\nbrains during cooperation. Also, we intended to explore arousal-related peripheral\r\nresponses during the task. To explore these issues, 14 participants paired as 7 dyads\r\nwere recorded with dual-EEG and dual-fNIRS setups while they were engaged in an\r\nattentive task finalized to engage cooperation. After a resting period which served as\r\ncontrol condition, the task was sub-divided in 8 blocks with a pause halfway assessing\r\nthe goodness of the cooperation scores. Thus, inter-brain activity coherence over\r\nthe prefrontal regions was calculated between the two participants across blocks. We\r\nfound that the coherence between the two signals varied across blocks in accordance\r\nto the perceived degree of cooperation. Such differences point toward a modulation\r\nbetween the two subjects’ brain activity as a function of the task, with respect to control\r\nconditions. This work represents the first use of dual-EEG/dual-fNIRS setups\r\nfor simultaneous measurements of brain-to-brain coupling and endorses the use of\r\nhyperscanning techniques for social interactive studies in naturalistic environments.