Fig. 2.

Differential Heartbeat-Evoked Responses (HERs) for imagining oneself (Self) or a friend (Other). A, Topographical map of the HER difference between Self and Other conditions, grand-averaged across 23 participants, in the 307–326 ms time window in which a significant difference was observed (Monte-Carlo p = 0.012). White dots represent the sensors contributing to the significant cluster. B, Time course of the HER (±SEM) for Self and Other, averaged over the sensors marked in white in A. The signal that might be residually contaminated by the cardiac artefact appears in lighter color and was not included in the epoch analyzed. The grey area represents the time window in which a significant difference was observed. C, Temporal evolution of the HER effect, during the imagination period. Amplitude in cluster corresponds to the average brain activity in the T-peak locked time window and sensors revealing a significant HER effect (sensors indicated in A, time window indicated in B). Cluster amplitude was computed for HERs occurring during fixation (1–1.3s), and during the imagination period divided in five windows of 1 second (1–2s, 2–3s, 3–4s, 4–5s, 5–6s). The largest cluster amplitude differences between Self and Other were observed in the windows 2–3s and 3–4s. D, Correlation between the size of the HER effect and Daydreaming Frequency Scores (p = 0.049). HER effect was computed for each participant as the difference between the HER cluster amplitude for Self minus the HER cluster amplitude for Other, z-scored across participants, for HERs in 2–4s of imagination period. Each dot represents one participant. **: p < 0.01, *: p < 0.05, (*): p < 0.1.