Simultaneous EEG-PET-MRI identifies temporally coupled, spatially structured hemodynamic and metabolic dynamics across wakefulness and NREM sleep

Sleep entails significant changes in cerebral hemodynamics and metabolism. Yet, how these two processes evolve throughout wakefulness and sleep and their spatiotemporal dependence remain largely unknown. By integrating a new functional PET technique with simultaneous EEG-fMRI, we reveal a tightly coupled temporal evolution of global hemodynamics and metabolism during the descent into NREM sleep, with large hemodynamic fluctuations emerging as global glucose metabolism declines, both of which track EEG arousal dynamics. Furthermore, we identify two distinct network patterns that emerge during NREM sleep: an oscillating, high-metabolism sensorimotor network remains active and dynamic in NREM sleep, whereas hemodynamic and metabolic activity in the default-mode network is suppressed. These results elucidate how sleep produces a loss of awareness while preserving sensory responses, and uncover a complex, alternating balance of hemodynamic and metabolic dynamics in the sleeping brain.