Cardiac interoceptive attention and the respiratory phase modulate heartbeat-evoked oscillations

Abstract: Heartbeat-evoked potentials (HEPs) are EEG voltage fluctuations reflecting the cortical processing of cardiac signals. In the time-frequency domain, recent studies have observed significant heartbeat-evoked oscillations (HEOs) both at rest and during tasks involving bodily self-awareness. In the time domain, our recent findings indicated heightened HEP positivity during exhalation compared to inhalation in a task centred on attending to cardiac sensations, likely indicating increased cardiac interoceptive attention. Here, we aimed to explore whether HEOs can be influenced by cardiac interoceptive attention and the respiratory phase. We examined HEOs (heartbeat-evoked power and inter-trial coherence) across the respiratory cycle in healthy volunteers at rest, during a cardiac interoceptive task (Heartbeat Counting Task, HCT), and during its exteroceptive control condition. We observed a significant increase in power and inter-trial coherence evoked by the heartbeat in theta and alpha bands during exhalation compared to inhalation, specifically during HCT. These findings support previous results demonstrating the impact of respiration on modulating cardiac interoception and suggest that alterations in HEOs in the alpha band may be linked to the selective inhibition or disengagement from competing or distracting exteroceptive stimuli outside the focal point of attention, particularly during exhalation.