Dynamic phase synchronization within the brain–heart-vascular network

The brain–heart axis arises from a bidirectional systems interaction mediated by vagal and sympathetic pathways, together with mechanical and baroreflex feedback loops. Although these dynamics have been investigated using a range of signal-processing approaches, it remains unclear whether they synchronize through phase locking mechanisms. Here, we test the hypothesis that cortical and cardiovascular interactions display phase synchronization. To this end, electroencephalogram (EEG), electrocardiogram (ECG), and blood pressure (BP) signals were recorded from 27 healthy subjects during rest and upright conditions. Time-resolved EEG power series were derived for canonical frequency bands, while the series of intervals between two consecutive R waves (RR intervals) was obtained from the ECG. Dynamic EEG-RR and EEG-BP phase synchronization was quantified using mean phase coherence (MPC), and the estimates were validated through surrogate data analysis. Significant EEG-RR coupling was observed in the high-frequency band of heartbeat dynamics, reflecting parasympathetic modulation, especially in resting conditions. Changes in EEG-BP synchronization were mainly sustained by cardiovascular oscillations in the low-frequency band during standing, consistent with enhanced sympathetic and baroreflex activity. These results reveal frequency-dependent phase synchronization within a healthy central-autonomic brain network and demonstrate the dynamic integration of central and peripheral oscillations. Phase-locking values such as MPC provide a robust quantitative framework for characterizing physiological brain–heart-vascular networks and may serve as valuable tools for investigating pathophysiological states.