Extracellular Volume Change in Human Brains during Sleep: A Simultaneous Sodium (23Na) MRI and EEG Study

Motivation: Alzheimer's disease is associated with neurotoxic amyloid-beta(Aβ) plaques. Studies in mice demonstrate that impaired cerebrospinal fluid(CSF) clearance reduces Aβ clearance by 70%. Sleep enhances CSF clearance by expanding extracellular space. Goal(s): However, the impact of sleep on extracellular volume change remains unclear in human brains due to a lack of non-invasive technology. Approach: To address this gap, we use sodium(23Na) MRI to measure the extracellular volume fraction in 16 healthy human brains. We monitor the sleep stage with MRI-compatible Electroencephalography(EEG). Results: On average, a decrease in extracellular volume fraction was observed in the gray matter significantly, but not significant in the white matter. Impact: Our research may shed light on how sleep may facilitate Aβ clearance in humans, bridging the gap between animal and human studies.