The cooperative social brain: EEG/fNIRS hyperscanning during a joint performance

Understanding the brain dynamics during social interaction has become an important issue for neuroscience research, and brain-to-brain coupling has sought to overcome some limitations of previous approach based on single-person recording. In fact, such studies cannot assess the dynamics of two (or more) brains interacting together, nor reproduce ecological settings. In the present study the neural basis of inter-brain cooperation underlying the execution of joint-actions were explored by using a hyperscanning paradigm involving both Electroencephalographic (EEG: experiment 1) and functional Near-Infrared Spectroscopy (fNIRS: experiment 2) coherence measures. Participants grouped in couples were asked to perform an attentional task in the form of a cooperative game. Synchronicity of the behavioral variables (Response Times, RTs, and Error Rates, ERs) was also considered during some steps of progressive social reinforcing conditions. In fact, during the task, subjects constantly received a feedback manipulated a priori to stress their good synchronizing abilities. Considering both EEG and fNIRS measures, the induced feedback affected both the cognitive performance and brain-to-brain coupling by increasing behavioral and brain synchronization when a positive reinforce was furnished to the participants. For what concerns EEG, high coherence effect was mainly observed when a positive reinforce was produced, but only for low frequency bands within the prefrontal left area, compared to the right one, thus underlining a left lateralization effect. Similarly, an increased brain activity over the prefrontal area was found for fNIRS measures in relation to the positive social feedback. Therefore, it is possible to hypothesize that the role of left PFC is significant induced by the positive reinforce, probably in relation to the perception of social efficacy in cooperative behavior. Finally, the cognitive and cortical coherence measures were shown to be correlated each other. These results underline the importance of simultaneously record brain dynamics in real-time interacting participants for studies on social cognition.