Hierarchical systems in the default mode network when reasoning about self and other mental states

Humans spend considerable time contemplating the minds of others. But this ability is not limited to external agents-we also turn the lens for reading minds inward, reflecting on our own thoughts, emotions, and sense of self. Some processes involved in reasoning about minds may rely on shared mechanisms, while others may be specific to the agent under consideration. We developed a paradigm where participants performed either a mental state inference task or a control task targeting either another person presented onscreen or their own mind. Using functional MRI and multi-voxel pattern analysis, we replicate a well-established self-other gradient along the medial prefrontal wall: ventral regions encoded mental state inference patterns for self, but not other, whereas more dorsal regions encoded mental state inference for both self and other, compared to control conditions. Posterior cingulate cortex, on the other hand, differentiated the target of mental state inference. Using a cross-classification analysis, we also found that patterns in the dorsomedial prefrontal cortex, ventromedial prefrontal cortex, and right temporoparietal junction were sensitive to mental state reasoning, regardless of the target agent. Our findings reveal a functional hierarchy for mental state reasoning where certain areas support agent-specific reasoning and others support more abstract, agent-general reasoning.