Cerebral and Peripheral Hemodynamics Across Wakefulness and NREM Sleep

Wake/sleep-related changes in cerebral hemodynamic oscillations are well established, but similar changes in peripheral hemodynamics remain largely understudied. Moreover, how the relationship between cerebral and peripheral hemodynamics varies across sleep-wake states is not well understood, despite evidence that these oscillations in the low-frequency range are strongly coupled during wakefulness. In this study, we investigated the temporal and spectral characteristics of cerebral and peripheral hemodynamics, as well as their low-frequency coupling, across sleep and wake states. To this end, we simultaneously measured cerebral hemodynamics using functional magnetic resonance imaging (fMRI) of the brain and peripheral hemodynamics using near-infrared spectroscopy (NIRS) of the fingertips in 10 healthy participants (6 females; age 19-24 years, mean ± SD: 20.90 ± 1.59 years) during wakefulness and non-rapid eye movement (NREM) sleep. Our results show that during sleep, cerebral hemodynamics differ markedly from peripheral hemodynamics in both oscillation amplitude and spectral power. Furthermore, low-frequency coupling between cerebral and peripheral hemodynamics becomes desynchronized during NREM3 sleep. These findings support the notion that NREM3 sleep plays a key role in the optimal restoration of cerebral vasomotion.