Individual differences in physiological adaptation correlate with cardioceptive precision in the heart rate discrimination task

Interoception, the process through which the organism senses internal bodily signals, is most commonly studied across the cardiac domain, yet the physiological basis of cardioception remains only partially understood. Moreover, most research has assessed cardiac interoception at rest, neglecting its dynamic nature.Here, we used the Heart Rate Discrimination (HRD) task to examine individual differences in cardiac physiology associated with interoceptive precision, particularly through ethanol-induced physiological modulation. In a double-blind within-subjects design, 36 participants completed the HRD at baseline and after consuming an alcohol or placebo beverage. Cardiac indices such as high-frequency and 0.1 Hz heart rate variability (HRV), heart rate baroreflex sensitivity (HR-BRS), and mean heart rate, were recorded before and after beverage administration. Preregistered baseline analyses showed no associations between baseline cardiac physiology and HRD precision. Exploratory analyses revealed selective associations for other HRD metrics: HF HRV correlated negatively with metacognitive sensitivity, while interoceptive threshold correlated negatively with mean heart rate and positively with HR-BRS. Crucially, preregistered mixed modelsshowed that within-subject increases in 0.1 Hz HRV positively correlate with interoceptive precision across both alcohol and placebo sessions.Our findings show differential physiological pathways feeding into different components of cardioception, as measured with the HRD. Additionally, the main effect of 0.1Hz HRV modulation on cardioceptive precision highlights the need for measuring interoceptive processes under physiological change.