Human brain solute transport quantified by glymphatic MRI-informed biophysics during sleep and sleep deprivation
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Abstract
Whether you are reading, running or sleeping, your brain and its fluid environment continuously interacts to distribute nutrients and clear metabolic waste. Yet, the precise mechanisms for solute transport within the human brain have remained hard to quantify using imaging techniques alone. From multi-modal human brain MRI data sets in sleeping and sleep-deprived subjects, we identify and quantify CSF tracer transport parameters using forward and inverse subject-specific computational modelling. Our findings support the notion that extracellular diffusion alone is not sufficient as a brain-wide tracer transport mechanism. Instead, we show that human MRI observations align well with transport by either by an effective diffusion coefficent 3.5 $$\times $$ × that of extracellular diffusion in combination with local clearance rates corresponding to a tracer half-life of up to 5 h, or by extracellular diffusion augmented by advection with brain-wide average flow speeds on the order of 1–9 $$\mu $$ μ m/min. Reduced advection fully explains reduced tracer clearance after sleep-deprivation, supporting the role of sleep and sleep deprivation on human brain clearance.
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Almost all experiments that have been interpreted as showing that sleep or anesthesia change brain clearance have involved introducing markers into the CSF, which then move into the brain parenchyma, confounding quantification of clearance.
“Indeed, almost all the experiments that have been interpreted as showing that sleep or anesthesia change brain clearance have involved introducing markers into the CSF, which then move into the brain parenchyma14,26–30. Under these circumstances, entry, exit and redistribution of the marker are all occurring simultaneously, greatly confounding any quantification of clearance.”
From Brain clearance is reduced during sleep and anesthesia (2024) · cites this paper as [29]
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“ISF bulk flow or CSF/ISF PVS flow [8, 27], and the associated term thus models solute advection.”
BackgroundSleep Drives Metabolite Clearance from the Adult Brain
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“In particular, extra426 cellular volume fraction, perivascular intake and interstitial 427 clearance (15), lymphatic efflux (16), choroid plexus gene 428 expression (65), AQP4 polarization and drainage to lymph 429 nodes (66), perivascular pulsations (67) all display significant 430 variations.”
BackgroundBrain-wide glymphatic enhancement and clearance in humans assessed with MRI.
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Sorted by citations
Brain clearance is reduced during sleep and anesthesia
Miao, A., Luo, T., Hsieh, B., Edge, C. J., Gridley, M., Wong, R. T. C., Constandinou, T. G., Wisden, W., & Franks, N. P. (2024) · Nature Neuroscience · doi:10.1038/s41593-024-01638-y · Cited by 172 · see citing works
- Authors
- Vinje, V., Zapf, B., Ringstad, G., Eide, P. K., Rognes, M. E., & Mardal, K.-A.
- Venue
- Fluids and Barriers of the CNS
- Published
- 2023-08-18
- Volume
- 20
- Issue
- 1
- ISSN
- 2045-8118
- PMC
- PMC10439559
- Cited by
- 81
- References
- 10
- Language
- en
- Funders
- Research Council of Norway (301013, 324239)
- national infrastructure for computational science in Norway, Sigma2 (NN9279K)
- European Research Council (714892)
- University of Oslo
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