Neural responses to heartbeats as a mechanism for distinguishing self from other during imagination
Imagination is an internally-generated process, where one can make oneself or other people appear as protagonists of a scene. How does the brain tag the protagonist of an imagined scene, as being oneself or someone else? Crucially, neither external stimuli nor motor feedback are available during imagination to disentangle imagining oneself from imagining someone else. Here, we test the hypothesis that an internal mechanism based on the neural monitoring of heartbeats could distinguish between self and other. 23 participants imagined themselves (from a first-person perspective) or a friend (from a third-person perspective) in various scenarios, while their brain activity was recorded with magnetoencephalography and their cardiac activity was simultaneously monitored. We measured heartbeat-evoked responses, i.e. transients of neural activity occurring in response to each heartbeat, during imagination. The amplitude of heartbeat-evoked responses differed between imagining oneself and imagining a friend, in the precuneus, mid and posterior cingulate regions bilaterally. Effect size was modulated by the general daydreaming frequency of participants but not by their interoceptive abilities. These results could not be accounted for by other characteristics of imagination (e.g., the ability to adopt the perspective, valence or arousal), nor by cardiac parameters (e.g., heart rate) or arousal levels. Heartbeat-evoked responses thus appear as a neural marker distinguishing self from other during imagination.\n\nHighlights- Heartbeat-evoked responses differentiate self from other during imagination.\n\n- These effects were located in the precuneus and mid- to posterior cingulate.\n\n- The neural monitoring of the body could be a mechanism for self/other distinction.