Plate Nº 28 · recorded September 29, 2026
Neuroscience & MindReported finding
Pink Noise Bursts May Boost the Brain's Nightly Wash Cycle
MIT researchers delivered precisely timed bursts of pink noise to sleeping volunteers and strengthened the fluid waves that flush waste from the brain, a possible step toward better sleep.
By Elena Vasquez4 min read861 words
In brief
- Fifty-millisecond bursts of pink noise, timed to slow-wave peaks, increased the amplitude of both slow brain waves and cerebrospinal fluid waves in 14 healthy sleepers.
- The study appears in Science Translational Medicine; senior author Laura Lewis and lead author Joshua Levitt developed fast EEG noise-filtering and a prediction algorithm to time the stimuli during simultaneous fMRI.
- The researchers have not yet shown cognitive or disease benefits — future work will test effects on insomnia and on protein-buildup diseases such as Alzheimer's.
A short burst of soft, staticky sound may be enough to strengthen the brain's nightly cleaning cycle. MIT researchers report that delivering 50-millisecond pulses of so-called "pink noise" at just the right moment during sleep increases the size of both slow electrical brain waves and the waves of fluid that wash waste out of the brain.
The findings, published in Science Translational Medicine, come from tests on 14 healthy volunteers. The researchers caution that the work is preliminary — the sample was small, all participants were healthy adults, and the study did not test whether the enhanced fluid flow actually improves health outcomes. But the results open a possible route toward more restorative sleep and, eventually, new approaches to diseases linked to harmful protein buildup in the brain.
Why the brain needs a wash cycle
During the day, the brain accumulates waste products such as lactic acid and worn-out proteins. At night, waves of cerebrospinal fluid — a clear liquid that surrounds and cushions the brain and spinal cord — help flush that waste away. This fluid also delivers nutrients like glucose to brain cells.
In 2019, Laura Lewis, now the Athinoula A. Martinos Associate Professor of Electrical Engineering and Computer Science at MIT, reported a method for measuring these fluid waves during sleep using functional magnetic resonance imaging (fMRI). That earlier work showed the waves are tightly coupled with slow electrical brain waves, the signature of deep, non-REM sleep.
For the new study, Lewis and her team wanted to know whether they could manipulate those brain waves — and thereby boost the fluid flow.
Pushing a swing at the right moment
Earlier research had shown that a sound delivered at the peak of a slow wave can deepen it. "Similar to a child on a swing, if you push them when they're at the right moment in their movement, you can make that swing go farther," Lewis says. "The challenge is: How do you find just the right time?"
The stimulus the team used is pink noise. Like white noise, it contains all frequencies audible to the human ear, but the lower pitches are louder and the higher pitches softer — producing a balanced, gentle sound similar to steady rain or a distant waterfall. At the volume used, it does not wake a sleeping person.
Timing the bursts required solving a technical puzzle. The researchers needed to record each sleeper's EEG — the brain's electrical signals — while simultaneously running an fMRI scanner to track fluid movement. The scanner's magnetic fields interfere with EEG signals. So the team developed a method to strip out that interference in under 100 milliseconds, plus an algorithm that predicts when the next slow-wave peak will arrive, compensating for the small processing lag.
What they saw
When the precisely timed bursts arrived, both the slow electrical waves and the cerebrospinal fluid waves grew larger in amplitude. The fMRI recordings also revealed a mechanism: slow waves make blood vessels constrict and dilate, so the vessels act like a pump that drives fluid out of the brain. Slow waves appear only during non-REM sleep and grow more pronounced in its deeper stages.
"We found that we were able to increase the size of the CSF flow wave during sleep, which as far as we know, there hasn't been a method to do before," Lewis says. "Now that we can enhance CSF flow during sleep in healthy adults, we're really excited to bring this technology to clinical populations to see what effects we can have."
Lewis is the senior author of the study. The lead author is Joshua Levitt, who recently completed his PhD at Boston University and worked as a visiting graduate student in Lewis's lab.
Next steps — and reasons for caution
The researchers now want to test whether boosting fluid flow can make sleep more restorative, particularly for people with insomnia. They also plan to examine whether speeding up the removal of brain waste could help people with Alzheimer's and other diseases marked by the accumulation of harmful proteins.
"Brain waste clearance is really important for Alzheimer's and other forms of dementia, which are caused, in part, by the buildup of molecules like amyloid and tau in the brain," Levitt says. "If we can improve brain waste clearance, we may be able to help prevent the buildups of these plaques that lead to disease."
Those applications remain hypotheses for now. This study involved only 14 healthy volunteers in a laboratory setting, and it did not measure cognitive or long-term effects. The link between enhanced fluid flow and disease prevention, while biologically plausible, still needs clinical testing.
Levitt has founded a company aiming to develop a home-use device, such as a headband, that would deliver auditory stimuli at the right moment to increase fluid flow.
The research received funding from the National Institutes of Health, the Simons Foundation Collaboration on Plasticity in the Aging Brain, the McKnight Scholar Award, a Sloan Fellowship, a Pew Biomedical Scholars Award, the MIT EECS Transformative Research Fund, the Corundum Convergence Institute, and the Panasonic Well Fellowship for AI and Wellness.
via science.org (Original)