VOLUNTARY BREATHING MODULATES HEARTBEAT-EVOKED CORTICAL DYNAMICS IN HUMANS

The cardiovascular and respiratory systems are anatomically and functionally integrated within the cardiorespiratory system at the peripheral level. This close connection is typically manifested through respiratory sinus arrhythmia, wherein heart rate accelerates during inhalation and decelerates during exhalation. Given that cardiac and respiratory signals can separately modulate brain rhythms and ultimately influence how individuals adapt to their environment, a critical question emerges: Do these cardiorespiratory interactions manifest at the cortical level beyond their peripheral coupling? Breathing is a flexible process that can be partially controlled voluntarily. This study leveraged this unique characteristic to probe how breathing coordinates heartbeat-evoked cortical activity. Participants performed normal-paced or slow-paced breathing at rest while cardiac, respiratory, and magnetoencephalography activities were simultaneously recorded. By averaging MEG signals time-locked to the R-waves in cardiac signals, heartbeat-evoked fields showed no differences according to breathing rate. Time-frequency analysis, however, demonstrated that, relative to slow-paced breathing, normal-paced breathing was associated with stronger cardio-cortical coupling in the alpha frequency band over temporoparietal sensors during the expiratory phase. Additionally, alpha-band coupling was greater during exhalation than inhalation under normal-paced breathing, an effect not observed during slow-paced breathing. Together, this study manipulated breathing rates to identify and perturb the spatiotemporal networks underlying coupled respiration- and heartbeat-evoked brain activities, thereby revealing how these interactions dynamically unfold under different respiratory rhythms. These findings suggest that respiratory rhythms modulate cardiac-cortical communication through frequency-specific mechanisms, highlighting the intricate nature of heart-lung-brain triad integration at the neural level.