Modulation of heartbeat-evoked oscillations and connectivity by respiration and focus of attention

Heartbeat evoked potentials (HEPs) are EEG voltage fluctuations that reflect the cortical processing of cardiac signals. In the time-frequency domain, recent studies have observed significant heartbeat evoked oscillations (HEOs) and connectivity at rest and during a task involving bodily self-consciousness.1,2 In the time domain, we recently found higher HEP positivity during exhalation compared to inhalation in a task focused on attending to cardiac sensations, likely reflecting heightened cardiac interoceptive attention.3 Here, we aimed to investigate whether HEOs and functional connectivity can be modulated by cardiac interoceptive attention and the respiratory phase. We assessed HEOs (heartbeat-related power and inter-trial coherence) and network connectivity across the respiratory cycle in 28 healthy volunteers at rest, during a cardiac interoceptive task (Heartbeat Counting Task), and during its exteroceptive control condition (Cardiac-Tone Counting Task). We found a significant increase in power, inter-trial coherence, and synchronization between cortical regions evoked by the heartbeat in theta and alpha bands during exhalation compared to inhalation, specifically during the cardiac interoceptive task. These data corroborate previous results highlighting the capability of respiration to modulate cardiac interoception, offering significant insights for clinical interventions to improve self-regulation. These results also suggest that changes in HEOs and functional connectivity in the alpha band may be related to the selective inhibition or disengagement from competing or distracting exteroceptive stimuli that are outside the focus of attention, particularly during exhalation.