2016 Volume 59 Issue 3 Pages 274-282
Development of social cognition is embedded in real-time social interactions between individuals, i.e., inter-subjectivity. To depict its neural underpinning, we have conducted a multi-brain approach utilizing hyperscanning fMRI that enables depiction of the neural activities of the two brains during a real-time interaction, i.e., joint attention. Hyperscanning fMRI of pairs of adults performing joint attention showed inter-individual neural synchronization in the right inferior frontal gyrus after all of the task-related effects were modeled out. To explore how the joint attention and eye-contact generates the state of shared attention, we conducted hyperscanning fMRI in which pairs of participants performed a real-time mutual gaze, before and after the joint attention task. During the mutual gaze, eye-blink synchronization, a behavioral index of shared attention, increased after the joint attention. The increase of eye-blink synchronization correlated positively with the increase of inter-individual neural synchronization within the right inferior frontal gyrus during mutual gaze. This enhanced neural synchronization also correlated positively with enhanced eye-blink synchronization during the previous joint attention. Thus, shared attention is represented and retained by pair-specific neural synchronization of the right inferior frontal gyrus. Furthermore, we have also successfully treated the two brains as a single unit, in order to understand the neural substrates of inter-subjectivity. We will apply this “two-in-one” strategy to various behavioral milestones of the development of social cognition from mutual imitation to prosocial behavior. Our “two-in-one” strategy using hyperscanning fMRI will become an indispensable and ground-breaking method to open the new field of “inter-subjectivity” social neuroscience.
