Cardiac-Neural Temporal Coupling as a Candidate Biomarker of Self-Congruency

Self-congruency refers to the coherence between an individual’s emotional experience and their enacted behavior. Because discrepancies between internal states and outward actions (i.e., self-congruency) are linked to vulnerability in mental health, identifying physiological signatures associated with self-congruency may offer novel biomarkers for psychological well-being. Therefore, this study investigated whether temporal covariance between cardiac and neural activity reflects individual differences in self-congruency. Thirty-eight healthy adults underwent resting-state functional magnetic resonance imaging to quantify neural dynamics variability, while cardiac activity was recorded using photoplethysmography to derive heart rate variability (HRV) measures. Self-congruency was assessed using a graphic rating scale in which participants adjusted the spatial overlap between two circles representing their emotional experience and enacted behavior. Temporal coupling between cardiac HRV and regional BOLD activity was quantified using cross-covariance analysis across biologically plausible temporal shifts. At the group level, covariance predominantly reflected brain-to-heart influence, particularly within regions central to the neurovisceral integration model such as the ventromedial prefrontal and anterior cingulate cortices. In contrast, individuals with higher self-congruency displayed stronger heart-to-brain-directed interplay, especially within regions implicated in emotion regulation and empathy, including the right rostral middle frontal gyrus and supramarginal gyrus. These findings indicate that although top-down regulation characterizes global heart-brain dynamics, greater alignment between emotional experience and enacted behavior is associated with increased bottom-up cardiac influence on neural activity. Given the relevance of both heart-brain communication and self-congruency for mental health, these results suggest a potential physiological-psychological biomarker axis with implications for prevention strategies.