The neural basis of sharing information through goal-directed conversation: A hyperscanning functional magnetic resonance imaging study

The human brain maintains internal models of physical and social environments, representing an individual's "subjectivity". Through conversation, two or more individuals share their models and modify them based on the exchange, a process that represents and is referred to as "intersubjectivity." To investigate the neural substrates of this dynamic process, hyperscanning functional magnetic resonance imaging was conducted to test the hypothesis that Inter-Brain Synchronization (IBS) in the default mode network (DMN) is involved in representing intersubjectivity. Twenty-four Japanese-speaking participant pairs played maze games over a two-day period. Each participant pair received a different maze, i.e., a maze with a different pathway to its goal. Although pairs shared a maze, each participant in a pair had only partial knowledge of the maze layout and what they knew about the layout differed. Taking turns, participants moved their pieces to their goals. Since each had only partial information about the pathway, effective communication between partners was important. Behavioral data showed participants' conversation about potential maze piece moves significantly increased as the game proceeded, implying that the exchange for such information was critical. Correspondingly, the DMN increased task-related activation, including the dorsomedial prefrontal cortex (dmPFC) and the bilateral temporoparietal junction (TPJ), extending through the superior temporal sulcus to the temporal pole and the right middle frontal gyrus. Within these areas, the dmPFC and the right TPJ showed task- and partner-specific IBS throughout all games. Thus, the DMN is likely required for representing intersubjectivity, based on internal models shared through real-time conversations.