Cardio-respiratory interactions in interoceptive perception: The role of heartbeat-modulated cortical oscillations

The cardiovascular and respiratory systems are anatomically and functionally integrated, suggesting that breathing continuously influences cardiac interoception. Previously, we demonstrated that the heartbeat-evoked potential (HEP), a neural marker of cardiac signal processing, is modulated by respiration, with enhanced late HEP positivity and increased interoceptive accuracy during exhalation. Here, we reanalysed our previous dataset in the time–frequency domain to investigate heartbeat-modulated cortical oscillations across respiratory phases during rest, cardiac interoception (heartbeat counting), and an exteroceptive control task. During heartbeat counting, exhalation was associated with increased late heartbeat-modulated alpha- and theta-band power and inter-trial coherence over fronto-parietal electrodes, compared with inhalation. Heartbeat-modulated alpha activity was related to HEP amplitude and predicted interoceptive accuracy. Exploratory analyses also indicated enhanced heartbeat-modulated functional connectivity during exhalation. These effects could not be accounted for by cardiac physiology alone and were absent during exteroception. We propose a mechanistic account of cardio-respiratory interactions grounded in interoceptive predictive coding, suggesting that exhalation enhances precision-weighting of cardiac signals by facilitating attentional allocation to interoceptive signals and suppressing task-irrelevant distractions.