Sleep is known to increase the convection of interstitial brain metabolites along with cerebrospinal fluid (CSF). We used ultrafast magnetic resonance encephalography (MREGBOLD) to quantify the effect of sleep on physiological (vasomotor, respiratory and cardiac) brain pulsations driving the CSF convection in humans. Transition to electroencephalography verified sleep occurred in conjunction with power increase and reduced spectral entropy (SE) of physiological brain pulsations. During sleep, the greatest increase in spectral power was in very-low frequency (VLF < 0.1 Hz) waves, followed by respiratory and cardiac brain pulsations. SE reduction coincided with decreased vigilance in awake state and could robustly (ROC 0.88, p < 0.001) differentiate between sleep vs. awake states, indicating the sensitivity of SE of the MREGBOLD signal as a marker for sleep level. In conclusion, the three physiological brain pulsation contribute to the sleep-associated increase in glymphatic CSF convective flow in an inverse frequency order.
bioRxiv Subject Collection: Neuroscience