Cerebrospinal fluid flushes waste from your brain during sleep

Your brain moves through four distinct sleep stages every night

Each stage plays a key role in memory, repair, restoration, and other key biological functions. The full cycle generally proceeds from light sleep and deep rest into vivid REM dreaming, which repeats between three and five times nightly.

The brain consolidates memories during sleep

During sleep, the brain appears to process memories from the day and encode them into long-term storage. At the same time, the brain prunes old memories out of the brain that are no longer useful. Understanding this process also sheds light a various neurodegenerative diseases.

Face and neck massages improve the removal of brain cell waste products in mice

A study identified that massaging mice and monkeys' faces and necks enhanced the flow of cerebrospinal fluid. Because CSF has been shown to flush out proteins linked to Alzheimer's and Parkinson's, the research hints at non-invasive treatments to reduce the severity of these diseases.

Researchers believe the brain consolidates memories, processes emotions, and plans for the future during dream states

Sharp wave ripples in the brain tag experiences for long-term memory storage

These ripples were known to quickly replay neuronal sequences during sleep for consolidation. While awake, they help the brain prioritize memories to remember, and their disruption can impair memory formation.

Studies suggest when you sleep is as important as how much you get

"Molecular clocks" made of timekeeping proteins and genes help regulate the body and its processes, meaning the disruption of one cog will impact another. Those who live in sync with their circadian rhythms report less fatigue, clearer thoughts, greater medication benefits, and better long-term health outcomes.

Studies suggest when you sleep is as important as how much you get, and syncing with your circadian rhythms may lead to less fatigue and improved long-term health outcomes

What sleep is for and why you can’t live without it

Sleep is one of the most important needs that humans have. The body uses sleep as a time of restoration and rejuvenation, as body tissues repair themselves, growth hormones are released, and the process continues. Brain plasticity theorists believe that sleep is also used for the processing and consolidating of new memories.

The brain will attempt to rest itself in periods of chronic sleep deprivation

Skimping on sleep lengthens reaction times and blunts decision-making skills. At a certain point, the brain will try to sneak sleep where it can, shifting sections offline even as you remain awake. Going without sleep raises blood pressure, undermines the immune system, and increases one's risk of dementia.

What sleep loss does to the brain

Proteins in the brain perform various critical functions, such as helping neurotransmitters function or enabling electrical activity in the organ. These proteins must fold in specific ways to perform their duties, similar to paper airplanes. Sleep deprivation contributes to the gathering of misfolded proteins that aren't shaped correctly for their roles and so accumulate in undesired spaces, such as in the gaps between neurons.

Dreams largely occur during REM sleep (but not entirely)

Modern imaging tools have enabled scientists to carry out in-depth studies of brain activity during sleep. Researchers know dreams arise largely during REM, blending emotion-driven visual imagery, memory consolidation, and weak associations to help us make sense of experiences, regulate emotions, and prepare for future situations.

Why do dreamers twitch?

This thought-provoking piece highlights newer research suggesting sleep twitches may not be random dream leftovers, but instead a crucial way our brains map and understand our bodies. From sleeping rat pups to dreaming octopi, this biological mapping system appears universal across animal species.

Exercise improves brain blood flow, stimulates neural growth, and more

Exercise has dramatic effects on human biology, including reducing some of the long-term harms associated with chronic stress. Its effects are also pronounced in the brain, including improved memory retention, sleep, cognitive functioning, and more.

Explore a series of bedtime exercises to improve sleep

Low-impact, mindful movements can potentially help the body and mind relax before sleeping. Such exercises could be a helpful complement to regular exercise during the day.

Scientists are learning to guide your dreams using sound and touch

Researchers are using a technique called "targeted dream incubation"—where stimuli like sounds or vibrations are introduced as you drift off—to influence dream content and potentially improve creativity, memory consolidation, and PTSD treatment. With the same mechanism, companies could theoretically target sleeping consumers with brand suggestions while they're unaware and neurologically susceptible, or assist in reducing nightmares.

Sleep paralysis occurs when the body fails to 'unfreeze' in sync with waking

When the body falls into a deep enough phase of sleep, it paralyzes certain parts of itself so the brain can't force it to physically act out dreams. This well-known but little-understood phenomenon happens when the brain awakens early and typically results in haunting hallucinations and reports of supernatural terrors.

Sleep training: risks and benefits

Sleep training, which can range from implementing a nighttime routine to letting your baby cry it out, is controversial, but does it work? While dozens of studies have found sleep interventions to be effective, it appears that many of these studies...

Open brain surgery is not required for BCIs inserted via blood vessel injection

Synchron's brain-computer interface, the Synchron Switch, takes advantage of preexisting medical devices, such as stents and catheters. Cells grow over the device over a 90-day period, incorporating it into the vessel wall and minimizing clots.

Scientists are studying dying patients' brain activity in the final moments of life

In the final moments of life there are distinctive bursts of coordinated neural activity. Researchers are interested in parsing that data to better understand the dying process and also exploring how this data relates to our understanding of consciousness.

A closer look at why people snore

Snoring is simply noise caused by improper airflow during sleep—and while it’s something that most people will do at some point in their lives, it can also be indicative of larger health problems. Generally speaking, snoring occurs when soft...

Cold water swimming can induce positive stress

The tradition of cold water swimming (or taking a cold plunge, or even a cold shower) has been shown to release the same hormones triggered during a stress response. This can have the effect of increasing blood flow, improved mental acuity, and more.

What does blood do?

Blood's primary purpose is to ferry oxygen and nutrients to cells in need while collecting cell waste and byproducts for removal. It also enables the body's repair and immune systems to traverse our internal landscape to address cell damage or external invaders, such as viruses and parasites. Zooming out from the exact roles of blood's various cells, the fluid connective tissue also assists with maintaining homeostasis via temperature regulation and pH balance.

Take a quiz to discover your brain care score

Each year, nearly 800,000 Americans have a stroke. With such a high occurrence rate, you may be asking yourself what you could do now to prevent a future stroke. Researchers at Harvard collaborated to answer this question by coming up with a "Brain Care" scoring system. Take the quiz to learn the quality of your brain health today and pick up helpful insights to lower your risk of stroke and dementia well into the future.

The human body relaxes upon death, including the bowel and bladder, expelling urine and feces

Watch a hospice nurse walk through how death affects the human body and what to expect in the hours and days following the death of a loved one as the body breaks down.

Alzheimer's can lead to brain shrinkage, with an average of around 2% of volume reduction per year

Sewage on cruise ships is cleaned onboard by bacteria and advanced filtration systems

A cruise ship's onboard sewage plant processes black water, human waste or sewage, and gray water, wastewater from sinks, showers, and washing machines. Treated water is stored until the ship reaches a distance where it can legally discharge it.

A beginner’s guide to the brain

Small but powerful, the brain constitutes only about 2 percent of the human body. However, it runs jus about everything, day and night, all year round. Learn about the different parts of the human brain, as well as its unique defenses, like the blood brain barrier in this four-minute video.

The history of brainwashing in America

"Brainwashing" refers to a coerced shift in worldview, often associated with cults or oppressive totalitarian governments. Though such processes are not well understood on a neurological level, they hold an outsized role in public imagination, particularly in science fiction and dystopias. This article reviews the history of the term, first popularized by Edward Hunter in 1950, and the subsequent use of the approach in pop psychology, the CIA, and more.

Bone marrow (soft tissue found inside certain bones) generates roughly 500 billion new blood cells each day

Recent research found that the brain doesn't seem to massively rewire following amputation—upending earlier beliefs about the cause of phantom limb pain.

Against his wishes, Albert Einstein's brain was removed before his cremation, and the pathologist responsible stored it for decades in mason jars within a beer cooler.

Learn how your body is, scientifically, like a firework with its own slow, controlled burn.

The use of fungi to detoxify land and water—a process known as mycoremediation—has been used to clean up natural resources affected by the 2025 California wildfires.

Ebola infects and disables immune cells, triggering a cascade of events that leads to small blood clots throughout the body, weakening blood vessels and interrupting blood flow to key organs.

An investigation suggests a Scottish island became awash in forever chemicals via seafoam and seaspray—raising questions about what that means for the safety of other coastal areas.

Hookworm infection, though risky, may help fight certain autoimmune conditions by tamping down the immune system's inflammatory response.

Crows are believed to have intelligence on par with a seven-year-old child and demonstrate complex behaviors, from problem-solving with tools to recognizing human faces.

Visualize how CRISPR-Cas9—a type of immune system used by single-celled organisms to attack invasive viruses—targets and makes precise changes to a gene's DNA.

To reduce wrinkles in clothing, research recommends gentle wash cycles with more water and tumble drying with smaller loads and longer times.

Read a deep dive on the 'all-purpose healing' peptide BPC-157.

In recent years a child anxiety expert has created and tested a novel phobia and anxiety treatment approach for children, focused on changing how parents respond to the fears.

Netflix profits when you're not watching, and its movies are designed that way—read a detail-rich critical essay exposing lesser-known Netflix takes

Planarian flatworms are small, aquatic worms with exceptional regenerative capabilities. When cut, the worms can regenerate multiple bodies in a matter of weeks.

When you complete a CAPTCHA on a website to prove you are human, you may be unknowingly training algorithms for self-driving cars, whose systems require training data to help identify crosswalks, bicycles, and other outdoor objects.

The Dracula character, now seen as the vampire archetype, was inspired by a seafood-induced nightmare its creator experienced.

Stars appear to twinkle because turbulence in the motion of molecules in Earth's atmosphere causes light to bend and wiggle rapidly on its way to the surface—a phenomenon called scintillation.

Pure water does not conduct electricity because this flow of energy requires the movement of charged particles, and water is a neutral molecule.

In 1945, Surrealist artist Salvador Dalí and legendary animator Walt Disney began collaborating on a short film that was not completed until 2003, years after both men had died.

Legendary architect Frank Lloyd Wright designed the SC Johnson headquarters in Wisconsin, aiming to make a cathedral-like workplace

NBA superstar Victor Wembanyama spent the 2025 summer training with monks in central China to enhance his body and mind.