Home / Sleep News / What Do Our Brains Do While We Sleep? They Keep Us Healthy

What Do Our Brains Do While We Sleep? They Keep Us Healthy

Olivia Murillo

Written by

Olivia Murillo, Contributing Writer

Fact Checked Icon
Fact Checked

Our dedicated team rigorously evaluates every article, guide, and product to ensure the information is accurate and factual. Learn More

What exactly is going on in our brain when we sleep? New research from the University of Oulu in Finland has revealed more about how brain activity changes during sleep and what that means for us.

Prior studies have shown how brain activity supports our long-term health by “washing out” potentially harmful materials from the fluid that surrounds our brain. The Finland study, focusing on a sample of 25 healthy participants, is the first to home in on how activities such as brain pulsations work while we’re sleeping. The results may help drive a correlation between dementia, including Alzheimer’s disease, and why we need sleep.

What Are Brain Pulsations?

Brain pulsations refer to the rhythmic movement of fluid around the brain. We drive these pulsations when we breathe in and out, when our heart beats, and when our blood vessels open and narrow, according to the study. The movement these pulsations create helps replace the older fluid that continually forms around our brain throughout the day with fresher fluid. As we sleep, these pulsations wash out waste molecules.

Accumulation of these waste molecules can become toxic. They can damage our neurons’ ability to communicate properly. Too much build-up can lead to memory impairment over time. For example, one waste product called beta-amyloid can build up, clump together, and prevent neurons from connecting. This may trigger or worsen Alzheimer’s disease.

“Researchers found that the brain activity was stronger and more steady across the brain while the participants slept than when they were awake.”

In this study, researchers looked at study participants’ brain pulsations when they were awake and when they were asleep, using various imaging tests. Researchers found that the brain activity was stronger and more steady across the brain while the participants slept than when they were awake.

Some pulsations, especially those driven by breathing, became stronger in areas near the back of the brain. This was similar to brain activity called delta waves, which are found in deeper stages of sleep. Delta waves often are associated with the “flushing” of older fluid from around the brain.

This supports past studies showing that cerebrospinal fluid (CSF), which surrounds the brain and spinal cord, moves more intensely when we sleep.

According to the new study: “We suggest the physiological brain pulsations, alongside slow-wave electrophysiological changes in [non-REM] sleep, likely contribute to elevated CSF flow.”

What Does This Say About Our Sleep?

In short, the findings support the basic advice that getting enough sleep helps your brain work — and not getting enough can cause trouble. Other previous studies have found higher levels of beta-amyloid in brains after just one night of sleep deprivation. This may be because of the disruption of vital processes that occur during sleep.

If poor sleep hygiene disrupts our sleep, we also may face long-term consequences to our memory. The study is one of the first to look more closely at a possible cause-and-effect relationship between sleep and brain disease. While relatively small, this study helps researchers gain a greater understanding of how brain pulsations work in healthy people.

Future research may look elements such as:

  • Brain pulsations in people with brain disorders;
  • How their pulsations differ from healthy individuals; and
  • Whether pulsations are disrupted during sleep and affect the movement of fluid and waste products around the brain.

Brain activity helps researchers learn about the importance of sleep, as well as other factors. For example, a recent study from the University of Bern in Switzerland suggests that specific waves near the front of the brain are related to our risk tolerance in certain situations.

  • Was this article helpful?
  • YesNo

About Our Editorial Team

Olivia Murillo

Contributing Writer

Olivia is the lab administrator for Dr. Matthew Walker’s Center for Human Sleep Science at the University of California, Berkeley. She manages a longitudinal project studying sleep and cognition in healthy older adults and has assisted research investigating various detrimental effects of sleep deprivation in young adults.


+4  Sources
  • 1.
    Helakari, H., Korhonen, V., Holst, S. C., Piispala, J., Kallio, M., Väyrynen, T., Huotari, N., Raitamaa, L., Tuunanen, J., Kananen, J., Järvelä, M., Tuovinen, T., Raatikainen, V., Borchardt, V., Kinnunen, H., Nedergaard, M., & Kiviniemi, V. (2022). Human NREM Sleep Promotes Brain-Wide Vasomotor and Respiratory Pulsations. The Journal of Neuroscience, 42(12), 2503–2515.
  • 2.
    National Institute on Aging. What Happens to the Brain in Alzheimer's Disease? (Reviewed May 16, 2017). Retrieved April 5, 2022.
  • 3.
    Fultz, N. E., Bonmassar, G., Setsompop, K., Stickgold, R. A., Rosen, B. R., Polimeni, J. R., & Lewis, L. D. (2019). Coupled electrophysiological, hemodynamic, and cerebrospinal fluid oscillations in human sleep. Science (New York, N.Y.), 366(6465), 628–631.
  • 4.
    Shokri-Kojori, E., Wang, G. J., Wiers, C. E., Demiral, S. B., Guo, M., Kim, S. W., Lindgren, E., Ramirez, V., Zehra, A., Freeman, C., Miller, G., Manza, P., Srivastava, T., De Santi, S., Tomasi, D., Benveniste, H., & Volkow, N. D. (2018). β-Amyloid accumulation in the human brain after one night of sleep deprivation. Proceedings of the National Academy of Sciences of the United States of America, 115(17), 4483–4488.

Learn more about Sleep News