Exploring the connected brain by fNIRS: human-to-human interactions engineering

Functional Near Infrared Spectroscopy (fNIRS) is a relatively new neuroimagingtechnique adequate and useful for exploring neural activity in social contexts involving humaninteractions. Compared to functional Magnetic Resonance Imaging (fMRI), fNIRS is easy-to-usesafe, noninvasive, silent, relatively low cost and portable, and applicable to subjects of all ages, thusresulting in a good option for ecological studies involving humans in their real-life context.Moreover, by using hyperscanning technique, fNIRS allows recording the hemodynamic cerebralactivity of two interacting subjects in an ecological context or during a shared performance. Thus,moving from a simple analysis about each subject’s neural response during joint actions towardsmore complex computations makes possible to investigate brain synchrony, that is the if and howone’s brain activity is related to that of another interacting partner simultaneously recorded. Here,we discuss how connectivity analyses, with respect to both time and frequency domain procedures,permitted to deepen some aspects of inter-brain synchrony in relation to emotional closeness, and tohighlight how concurrent, cooperative actions can lead to interpersonal synchrony and bond constructio