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categories: ["longevity", "cybernetics"]categories: ["longevity", "cybernetics"]tags: ["sleep", "neuroscience", "dementia", "neurodegeneration", "amyloid", "neuromodulation", "brain"]tags: ["sleep", "neuroscience", "dementia", "neurodegeneration", "amyloid", "neuromodulation", "brain"]summary: "A proposed brain-wide waste-clearance route in which cerebrospinal fluid enters along arteries, mixes with interstitial fluid and drains away, shown in mice and disputed in mechanism."summary: "A proposed brain-wide waste-clearance route in which cerebrospinal fluid enters along arteries, mixes with interstitial fluid and drains away, shown in mice and disputed in mechanism."updated: "2026-10-28"updated: "2026-10-29"humanEvidence: "Contrast MRI shows tracer reaching the whole human brain and clearing more slowly after a sleepless night, and fMRI links CSF pulses to NREM slow waves; no study has shown that altering the pathway changes disease in people."humanEvidence: "Contrast MRI shows tracer reaching the whole human brain and clearing more slowly after a sleepless night, and fMRI links CSF pulses to NREM slow waves; no study has shown that altering the pathway changes disease in people."issues: ["Nedergaard group's 2025 mouse work on norepinephrine-driven vasomotion during sleep is not covered", "No coverage of human 40 Hz stimulation trials"]issues: ["Nedergaard group's 2025 mouse work on norepinephrine-driven vasomotion during sleep is not covered", "No coverage of human 40 Hz stimulation trials"]------lines 33–39 → 33–4019 unchanged lines not shown
between cells, and leaves along routes that drain towards lymph nodes in the neck. The name wasbetween cells, and leaves along routes that drain towards lymph nodes in the neck. The name wascoined in 2012 for a mechanism said to depend on water channels in astrocytes, a kind of glial cell.coined in 2012 for a mechanism said to depend on water channels in astrocytes, a kind of glial cell.That CSF enters brain tissue along blood vessels is well supported in rodents; whether fluidThat CSF enters brain tissue along blood vessels is well supported in rodents; whether fluidactually flows through the tissue, and whether sleep speeds it up, remain disputed as of October 2026.actually flows through the tissue, and whether sleep speeds it up, remain disputed as of October2026. ```keyfacts```keyfacts[[lines 96–108 → 97–11056 unchanged lines not shown
## Measuring it in people## Measuring it in people Human evidence rests on three indirect methods. The most direct is intrathecal-contrast MRI. Researchers in OsloHuman evidence rests on three indirect methods. The most direct is intrathecal-contrast MRI.injected the contrast agent gadobutrol into the CSF and scanned repeatedly over two days and againResearchers in Oslo injected the contrast agent gadobutrol into the CSF and scanned repeatedly overat four weeks; the tracer reached every brain region and cleared more slowly in patients withtwo days and again at four weeks; the tracer reached every brain region and cleared more slowly inidiopathic normal pressure hydrocephalus, a condition that causes dementia. In a follow-up, onepatients with idiopathic normal pressure hydrocephalus, a condition that causes dementia. In anight of total sleep deprivation in seven people slowed tracer clearance from most brain regionsfollow-up, one night of total sleep deprivation in seven people slowed tracer clearance from mostcompared with seventeen who slept, and a further night of sleep did not make up thebrain regions compared with seventeen who slept, and a further night of sleep did not make up thedifference.[^ringstad2018] The method shows where a tracer goes, not by what physical process.difference.[^ringstad2018] The method shows where a tracer goes but not which physical processcarries it there. Fast functional MRI is the second. A 2019 study of thirteen sleeping volunteers found that duringFast functional MRI is the second. A 2019 study of thirteen sleeping volunteers found that duringnon-REM sleep neural slow waves were followed by oscillations in blood volume, which werenon-REM sleep neural slow waves were followed by oscillations in blood volume, which werelines 130–136 → 132–13821 unchanged lines not shown
brain tissue of male mice and reported that its movement was independent of sleep, waking andbrain tissue of male mice and reported that its movement was independent of sleep, waking andanaesthesia, while clearance was markedly reduced during sleep and anaesthesia.[^miao2024] Inanaesthesia, while clearance was markedly reduced during sleep and anaesthesia.[^miao2024] In2025, Nedergaard's group argued that the study measured movement of dye within the brain rather2025, Nedergaard's group argued that the study measured movement of dye within the brain ratherthan its removal, that the dye crosses the blood–brain barrier, and that the anaesthetic was giventhan its removal, that the dye crosses the blood-brain barrier, and that the anaesthetic was givenonce and mostly wore off. Franks and Wisden replied that all of the objections wereonce and mostly wore off. Franks and Wisden replied that all of the objections were"misunderstandings, misleading, or simply incorrect", and countered that most studies reporting"misunderstandings, misleading, or simply incorrect", and countered that most studies reportingfaster clearance during sleep actually measure tracer entering the brain from the CSF, which theyfaster clearance during sleep actually measure tracer entering the brain from the CSF, which theylines 147–170 → 149–17410 unchanged lines not shown
## Alzheimer's disease, aging and brain injury## Alzheimer's disease, aging and brain injury The disease case rests almost entirely on mice. A 2024 study in 5XFAD mice, a strain engineered to accumulate amyloid, found that one-hour sessions ofThe disease case rests almost entirely on mice. A 2024 study in 5XFAD mice, a strain engineered to40 Hz flickering light and sound increased CSF influx and interstitial efflux in cortex, togetheraccumulate amyloid, found that one-hour sessions of 40 Hz flickering light and sound increased CSFwith more AQP4 polarization and wider meningeal lymphatic vessels. Inhibiting glymphatic clearanceinflux and interstitial efflux in cortex, together with more AQP4 polarization and wider meningealabolished the stimulation's reduction of amyloid.[^murdock2024]lymphatic vessels. Inhibiting glymphatic clearance abolished the stimulation's reduction ofamyloid.[^murdock2024] In October 2026 a Beijing group reported a similar result with 40.68 MHz ultrashort-waveIn October 2026 a Beijing group reported a similar result with 40.68 MHz ultrashort-waveradio-frequency energy, a physiotherapy modality, applied at a non-thermal setting throughradio-frequency energy, a physiotherapy modality, applied at a non-thermal setting throughelectrodes held 2 cm from the skull.[^liu2026] In healthy young male mice under anaesthesia for the tracer measurements, a singleelectrodes held 2 cm from the skull.[^liu2026] In healthy young male mice under anaesthesia for the10-minute session increased tracer arrival in cervical lymph nodes at 60 minutes; by 120 minutestracer measurements, a single 10-minute session increased tracer arrival in cervical lymph nodes atthe groups no longer differed. In awake mice, exposure raised delta-band power in hippocampal and60 minutes; by 120 minutes the groups no longer differed. In awake mice, exposure raised delta-bandEEG recordings. The tracer effect was blunted in a chemogenetically silenced hippocampus andpower in hippocampal and EEG recordings. The tracer effect was blunted in a chemogeneticallyabolished when AQP4 was blocked with a drug. After closed-skull brain injury, treated mice hadsilenced hippocampus and abolished when AQP4 was blocked with a drug. After closed-skull brainless brain water at one hour and three days. In six-month-old female 5XFAD mice, seven daily sessions improved tracer clearance, loweredinjury, treated mice had less brain water at one hour and three days. In six-month-old female 5XFADamyloid-β immunofluorescence (7–8 mice per group) and improved two memory tasks. The authors notemice, seven daily sessions improved tracer clearance, lowered amyloid-β immunofluorescence (7-8 micethat the whole experiment was run as one cohort without independent replication.per group) and improved two memory tasks. The authors note that the whole experiment was run as onecohort without independent replication. > [!caution] What the ultrashort-wave study did not show> [!caution] What the ultrashort-wave study did not show> Compressed into a headline, the study becomes a way to flush Alzheimer's plaque from the brain in> Reduced to a headline, the study reads as a way to flush Alzheimer's plaque from the brain in> minutes. It does not show that. The 10-minute effect was faster tracer drainage in healthy mice.> minutes. It does not show that. The 10-minute effect was faster tracer drainage in healthy mice.> The amyloid reduction followed a week of daily sessions in a mouse model and was a fall in> The amyloid reduction followed a week of daily sessions in a mouse model and was a fall in> staining intensity, not removal; tau was not measured. AQP4 was redistributed towards blood> staining intensity, not removal; tau was not measured. AQP4 was redistributed towards bloodremoved, struck through added, underlinedLine numbers count the serialised markdown of each revision, frontmatter included.
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