Cardiac-vagal rhythm echoes on the heartbeat's mechanosensory imprint in the brain.

The heart, a highly reactive and innervated organ, plays a crucial role in brain-viscera communications. Recent research has highlighted the role of mechanosensation in the brain, where ion channels in neurons' membranes respond to heartbeat-induced pressure changes, triggering specific neural responses. Cardiac mechano-electric coupling ensures cardiac output to match venous return through beat-by-beat feedback. However, the effect of ongoing cardiac rhythms on the brain-sensed strength of each heartbeat is not well understood. This is crucial for exploring brain-heart communication pathways and for understanding the mutual influence between brain and cardiac oscillations. This study explores how cardiac rhythms influence heartbeat strength (HBS) as detected by the brain in humans. As a proxy for brain-sensed HBS, we used ballistocardiographs, which capture HBS from the back of the head while participants are in horizontal position. By modeling HBS, we demonstrate that fast fluctuations in heart rate variability significantly influences the final HBS. This suggests a direct relationship between vagal tone and subsequent neural responses to heartbeats, highlighting the necessity of studying visceral oscillations in the context of mechanosensation and inter-organ communication research.