By JOSEPH STRONGOLI, Featured Columnist
Your brain’s workday consists of strenuous activities like information processing, perception, memory/recall, abstraction, recognition, emotion, interpretation and integration of data from the five senses, motor coordination, and subconsciously directing all your bodily processes based on constant feedback from all over your body. Phew.
All this work happens simultaneously, and can leave behind quite a mess of metabolites (the used up chemical byproducts of the brain at work). At the end of the day, your brain is left with quite a messy workplace, and until now, it hadn’t been clear just how the brain cleans up after itself.
Just how does the brain keep itself from becoming a "dirty mind"?
In a study published in the 2012 issue of Science Translational Medicine, a team of researchers led by Drs. Jeffrey Iliff and Maiken Nedergaard at the University of Rochester have discovered a plumbing system that washes brain tissue clean of its waste products, called the glymphatic system.
Talk about a brainwashing! The authors say that these findings could explain why sleep is so restorative, and why the lack of it is so detrimental to brain function.
These new findings also have promising implications for Alzheimer’s Disease and other dementia related to the buildup of toxic waste in the brain. Specifically, many scientists believe that Alzheimer's is caused by the failure of the brain to remove toxic tau proteins.
Cleaning Up After Yourself
Our bodies have a self-cleaning mechanism, the lymphatic system, which removes dead blood cells and other waste through a network of vessels. They are the clean-up crew, the body’s janitors if you will, sweeping up shop after another hard day of work making the body go.
The brain however, has a different method of keeping itself clean.
Thanks to the blood-brain barrier – a natural firewall that seals the brain off from the rest of the body, letting only certain authorized molecules pass – the brain is never touched by unfiltered blood, thus it remains safe from microbes, viruses, bacteria, and other pathogens.
Therefore, the brain is effectively sealed off from the rest of the body: authorized personnel only behind the blood-brain barrier.
But because of this, the brain is then also sealed off from the lymphatic system –not even the janitors are allowed into the Presidential Suite to clean up!
This architecture presents a mystery. How then, does the brain end each day elbow deep in its own waste, and wake up each morning scrubbed sparkly clean?
It has long been known that to transport nutrients to brain tissue and to remove waste, the brain makes a liquid called cerebrospinal fluid. But it hasn’t been clear how this special fluid removes the waste products and detritus generated by brain cells – until now.
Experiments in the 1950’s and 60’s hypothesized that diffusion (the passive way that liquids or gases spread out within their containers, due to kinetic energy) distributed cerebral spinal fluid throughout the brain. But diffusion proceeds way too slowly to keep up with the brain’s lightning-fast activity and to explain its pristine cleanliness.
It turns out that, while looking for the brain’s method of self-preening, researchers in the ‘50s and 60s unwittingly deactivated the plumbing that cleanses brain tissue: "The idea of a cleaning system based on pressure has been around for a long time, but if you open the skull anywhere, like a hydraulic pump, it stops. They thought [the cleaning system] didn't exist," said Dr. Nedergaard.
How Does the Glymphatic System Work? A True Brain Drain
Drs. Iliff and Nedergaard and their team used a technique called 2-photon laser scanning microscopy, whose infrared light allows a deep, clear look into living brain tissue without harming it.
They examined the flow of cerebral spinal fluid by injecting fluorescent tracer molecules into the spinal cord, to follow its path in real time in living mice brains, and what they found was truly astounding.
They watched as the tracer molecules flowed through a series of channels surrounding the blood vessels in the brain, called astrocytes.
Astrocytes are a type of glial cell, a class of cells that support neurons in the nervous system. These cells have protuberances called feet, which wrap around arteries and veins, like pipes wrapping around other pipes.
Miniscule pores in the outer pipe suck the nutrient-rich cerebral spinal fluid from the blood vessels into channels dense with nerve cells, and the fluid is then pumped out through other pores, simultaneously feeding the brain’s cells while removing its waste.
Nedergaard and Iliff dubbed the newfound waste removal system the glymphatic system, after glial cells and the lymphatic system.
The glymphatic system is “on the order of a thousand times faster than diffusion,’ says Dr. Nedergaard. “I’m surprised that no one had discovered this until now.”
Cleanliness is Braininess
What are the implications of these findings? The researchers speculated that a poorly functioning glymphatic system might lead to the accumulation of toxic waste in the brain.
In fact, such a buildup could lead to Alzheimer’s disease; patients with Alzheimer's tend to have an accumulation of a protein called amyloid beta in the brain, which causes cell damage.
The authors injected amyloid beta into the brains of both healthy mice and mice genetically modified to deactivate their glymphatic system.
The healthy mice removed the protein quickly and efficiently from their brain tissue. But the mice with the disabled glymphatic systems suffered much slower protein removal.
“This work shows that the brain is cleansing itself in a more organized way and on a much larger scale than has been realized previously,” Nedergaard says.
“We're hopeful that these findings have implications for many conditions that involve the brain, such as traumatic brain injury, Alzheimer's disease, stroke and Parkinson's disease.”
“Increasing the activity of the glymphatic system might help prevent amyloid deposition from building up,” says Iliff, “or could offer a new way to clean out buildups of the material in established Alzheimer's disease.”
Dr. Illif touches on an exciting and promising possibility. Could we enhance cognitive function by increasing/improving the activity of the glymphatic system?
What Factors Affect The Glymphatic System’s Performance?
There are a couple of ways to help your glymphatic system do its job, and in the process improve your brain’s overall function and reduce your risk for Alzheimer’s and other dementia related to toxic buildup in brain tissue.
The foremost way is to make sure you are getting your beauty rest.
A 2013 follow-up study by Drs. Illiff and Nedergaard and their team found that the glymphatic system runs twice as fast during deep sleep than during waking hours.
According to the authors, this could explain why sleep is restorative, and why the lack of sleep impairs brain function. While you are soundly snoozing your brain is still hard at work, cleaning up after the mess you made all day!
Sleep on Your Side to Clean Your Brain
Taking it a step further, a 2015 study found that even the position in which you sleep can affect your glymphatic’s system’s performance.
The authors examined the difference between sleeping in the supine (on your back), prone, (on your stomach), and lateral (on your side) positions.
The authors concluded that “glymphatic transport was most efficient in the lateral position compared with the supine or prone positions. In the prone position, in which the rat's head was in the most upright position (mimicking posture during the awake state), transport was characterized by “retention” of the tracer, slower clearance, and more CSF efflux along larger caliber cervical vessels.”
That’s right, sleeping on your side boosts your glymphatic system, because it alerts your brain to the fact that you are sleeping, which is the prime time for the glymphatic system to kick into gear, when your brain isn’t occupied by being awake.
Dr. Nedergaard says: "The brain only has limited energy at its disposal and it appears that it must choose between two different functional states — awake and aware or asleep and cleaning up. You can think of it like having a house party. You can either entertain the guests or clean up the house, but you can't really do both at the same time.”
The authors went on to say: “We propose that the most popular sleep posture (lateral) has evolved to optimize waste removal during sleep, as it mimics the natural resting/sleeping position.”
Drink More Water to Improve Your Brain's Ability to Dispose of Waste
Another way to improve glymphatic function is to stay hydrated. A 2014 study at the Patton State Hospital in California found that a properly hydrated brain enables both the clearance of molecular waste and the volume transmission of chemical symbols.
Conversely, a brain deprived of water led to the accumulation of misfolded proteins and neuroinflammation.
Hydrate well before you go to sleep, as 8 hours in bed without water is when we dehydrate the most.
Yoga Helps to Clean Your Brain?
Although there has yet to be any scientific studies providing solid evidence, many yoga gurus claim that certain yoga postures aim to facilitate the flow of CSF up and down the spine so that it can reach the brain stem.
The last way to improve help your glymphatic system? To be determined. These findings are still very new and cutting edge. This is exciting research that bears keeping an eye on, as the possibilities are promising: “these findings have significant implications for treating 'dirty brain' disease like Alzheimer's.
Understanding precisely how and when the brain activates the glymphatic system and clears waste is a critical first step in efforts to potentially modulate this system and make it work more efficiently," says Dr. Nedergaard.