Cardiac activity is associated with changes in microstates of the electroencephalogram

The brain and the heart communicate bidirectionally, primarily through the autonomic nervous system. Among the tools for investigating this interaction, electroencephalographic (EEG) microstates—quasi-stable scalp topographies reflecting global brain integration—can offer novel insights into brain-heart dynamics, which is scarce in the literature. This study investigated the relationship between microstates and cardiac activity by simultaneously recording EEG and electrocardiograms from 103 healthy participants during resting state. Our analysis revealed temporal associations between specific microstates and cardiac events: microstates A, D, and E showed distinct probability of occurrence throughout the cardiac cycle, with microstate A exhibiting increased probability during R and T waves of the electrocardiogram. Furthermore, the occurrence probabilities of microstates A and E varied with the phase of low-frequency heart rate variability (LF-HRV). These findings provide evidence for the coupling between peripheral cardiac processes and central brain activity, suggesting that EEG microstate patterns reflect cardiac-related activity.