Sleep deprivation (SD) significantly impacts brain function, particularly through disruption of the glymphatic system, an essential mechanism for cerebral metabolic waste clearance dependent on cerebrospinal fluid (CSF) dynamics. Recent advances link CSF flow to global brain activity, measurable via global blood-oxygenation-level-dependent (gBOLD) signals. However, how gBOLD-CSF coupling changes during prolonged wakefulness remains unclear. Using resting-state functional magnetic resonance imaging (rs-fMRI), we investigated how 36-hour sleep deprivation affects gBOLD-CSF coupling in healthy participants. We observed a significant transient increase in gBOLD-CSF coupling strength as sleep deprivation progressed, peaking after approximately 30 h of wakefulness. Importantly, changes in coupling strength correlated quantitatively with heightened subjective sleep pressure but not with vigilance performance. Furthermore, SD induced a temporary phase shift in CSF signal timing relative to gBOLD, indicating disrupted temporal coordination. These results suggest that SD triggers both a transient enhancement and a temporal instability in neuro-fluid coupling, reflecting a biphasic modulation of brain-CSF coupling linked to glymphatic-related dynamics. Our findings reveal novel compensatory adjustments within the glymphatic system during prolonged wakefulness, advancing our understanding of the physiological underpinnings linking sleep loss, metabolic clearance, and brain function, with potential implications for cognitive health and neurodegenerative disease risk.
Zhang et al. (Mon,) studied this question.