Minimal social co-presence modulates heartbeat evoked potentials and EEG dynamics during a parallel crafting task

OBJECTIVE: To investigate the neurophysiological effects of minimal social co-presence on the Heartbeat Evoked Potential (HEP) and EEG dynamics, providing a normative baseline for altered interoception in clinical disorders. METHODS: Thirty healthy adults performed a repetitive crafting task in "alone" and "parallel social presence" conditions. EEG and ECG were recorded, and HEPs plus time-frequency dynamics were compared using permutation testing. Changes in cardiac vagal activity and subjective stress were also assessed. RESULTS: Parallel co-presence significantly altered HEP morphology (reduced frontal negativity, central-parietal positivity) and EEG power (beta, theta, alpha bands). Only under parallel condition, frontal HEP amplitude correlated with increased cardiac vagal activity (r = 0.39) and reduced subjective stress (rS = -0.55). CONCLUSION: Minimal social context alters the brain's processing of cardiac signals and its autonomic relationship in healthy young adults, establishing a neurophysiological benchmark for brain-body-society interactions. As this study used a non-clinical sample, the findings are not direct evidence of HEP's clinical utility. This work provides a foundational baseline for future comparative studies needed to determine its potential as a clinical biomarker. SIGNIFICANCE: This study is the first to demonstrate normative neurophysiological effects of minimal social presence on HEP, providing critical evidence and guidance for future clinical research.