Vasomotor Pulsation Becomes a Driver of Cerebrospinal Fluid and Electrophysiological Dynamics in Sleeping Human Brain

Sleep is essential for maintaining brain tissue homeostasis, which is facilitated by enhanced cerebrospinal fluid (CSF) solute transport. Infra-slow (<0.1 Hz) vasomotion, CSF flow, and electrophysiological potential all increase during sleep, but their contributions as potential drivers of CSF flow in human brain remain unknown. To investigate this, we recorded the three signals in healthy volunteers across sleep-wake states using 10 Hz functional magnetic resonance imaging (fMRI BOLD), electroencephalography (DC-EEG), and functional near-infrared spectroscopy (fNIRS). We then analyzed the directed coupling patterns using phase transfer entropy (TE). In the awake state, electrophysiological potential and water concentration changes both predicted vasomotor waves across the brain, possibly reflecting functional hyperemia. During sleep, this coupling reversed, with vasomotor waves instead predicting electrical changes and CSF flow in cortical areas. Furthermore, we found that the amplitude of these dynamics increased during sleep, highlighting the critical role of physiological oscillations in sleep-associated brain fluid flow.