Two more than one. The effect of cooperation on intra- and inter-brain connectivity

Inter-brain synchronicity during joint actions is a core question of study on social interactions, but the specific contribution of intra and inter-brain functional connectivity still remains to be answered. Moreover, the intervention of psychological variables must be taken into account, such as self-perceived efficacy induced by an external feedback during interaction towards the adoption of common strategies. The cognitive performance and the neural activation underlying the execution of joint-actions were explored by functional Near-Infrared Spectroscopy (fNIRS) during a synchronicity game where dyads of participants received reinforcing feedbacks. Intra and inter-brain connectivity indices were computed, along with a ConIndex (inter-brain/intra-brain connectivity) within the prefrontal cortex. Finally, correlational measures were consideredto assess the relation between these different levels. Results showed that the external feedback was able to modulate participants’ responses in both behavioral and neural components with faster RTs after the reinforce and increased inter-brain connectivity and ConIndex, mainly localized within the DLPFC. Moreover, the presence of significant correlations between RTs and inter-brain connectivity revealed that only the “two-players connection” may guarantees an efficient performance. These results provided significant contribution to the identification of patterns of intra and inter-brain functional connectivity when social reinforce is provided within dyads of participants cooperating together.