Contents
Introduction: The Mechanism of Sleep and Brain Cleansing
Video courtesy of Laura Lewis: Waves of cerebrospinal fluid flow (blue) during sleep.
Recently, a study by Boston University【1】revealed some fascinating discoveries about how the brain refreshes itself during sleep.
Specifically, a special type of brainwave called slow waves (or delta waves) plays a crucial role during deep non-REM sleep.
These waves help to enhance the flow of a special fluid (cerebrospinal fluid) within the brain, effectively cleaning out unwanted substances.
In other words, sleep not only serves as rest but also plays an essential role in cleaning the brain.
In this article, we will explain in detail how these special brainwaves clean the brain and relieve fatigue.
Delta Waves Promote the Flow of Cerebrospinal Fluid (CSF)
Explanation of the Mechanism
Delta Waves and Decreased Brain Activity
During deep sleep, slow brainwaves (delta waves) appear. These brainwaves have a low frequency of 0.2–4Hz, indicating that the brain is in a state of deep rest. At this time, overall brain activity slows down (with neural activity being generally suppressed).
Changes in Brain Blood Flow and Blood Volume
As brain activity decreases, blood flow to the brain is reduced because the brain requires less oxygen while resting. With reduced blood flow, blood volume decreases, creating more space within the brain for cerebrospinal fluid to flow in.
Increased Flow of Cerebrospinal Fluid
This allows cerebrospinal fluid to circulate smoothly throughout the brain, effectively washing away unwanted substances.
【Fig. A,B,C,D,E】Fultz, N. E., et al. (2019). Coupled electrophysiological, hemodynamic, and cerebrospinal fluid oscillations in human sleep. Science.
In Simple Terms
In short, special brainwaves during deep sleep help the brain rest → reduce blood flow → improve cerebrospinal fluid flow → clean the brain.
Cerebrospinal Fluid (CSF) Resets Brain Fatigue
Causes of Brain Fatigue and Its Effects
What Is Brain Fatigue?
Our brain uses a lot of energy during the day, leading to the buildup of unwanted substances like amyloid-beta and tau proteins. When these accumulate too much, the brain becomes fatigued. These unwanted metabolic byproducts interfere with the normal function of nerve cells, reducing the efficiency of neural networks. As a result, cognitive functions and focus decrease, leading to what we call brain fatigue.
Reduced Focus and Decision-Making Caused by Brain Fatigue
When brain fatigue builds up, focus and decision-making abilities decline, and thoughts become less clear. When the brain feels fatigued, it can lead to decreased daily performance and increased stress and anxiety. This can cause more mistakes in daily life and reduced memory capacity.
Mechanism for Resetting Brain Fatigue
Cerebrospinal Fluid Cleans the Brain’s “Waste”
The increased flow of cerebrospinal fluid during deep sleep helps wash these substances away. During deep sleep, cerebrospinal fluid circulates throughout the brain, actively removing unwanted materials. This allows the brain to recover and process new information smoothly again.
Practical Tips for Ensuring Quality Sleep
Recommended Habits
Deep Breathing and Relaxation Effects
Deep breathing activates the parasympathetic nervous system, calming the heart rate and creating a relaxed state【2】. This helps ease the transition into sleep and promotes deep sleep. By continuing deep, slow breathing, the brain naturally relaxes and enters deep sleep.
Meditation and Mindfulness
Meditation not only calms the mind but also has positive effects on brainwaves. Even beginners can increase alpha waves (8–12Hz), which create a state of relaxation for the mind and body. Advanced meditators or long-term practitioners often see an increase in gamma waves (above 30Hz), which is associated with high levels of focus and unified awareness. This increase in gamma waves enhances the synchronization of neural networks and promotes overall harmony in the brain【3】【4】.
Conclusion: Unlock the Brain’s Healing Power with Delta Waves
Quality sleep, especially deep sleep, is essential for revitalizing the brain and making daily activities more fulfilling.
To make the most of the brain’s natural “cleaning” process, it’s important to pay attention to how you spend your time before bed. By making small adjustments to daily habits, your brain can feel more refreshed, and you can enjoy a more pleasant day-to-day life.
Through the explanations so far, we hope you have understood that sleep plays a crucial role beyond just resting. By leveraging the power of deep sleep, you can keep your brain healthy for the long term.
In fact, what your brain might truly need is that “brain cleaning time” that happens during quiet nighttime hours.
Make an effort to get quality sleep, and keep both your brain and body healthy for a more mindful and fulfilling life.
References
【1】Fultz, N. E., et al. (2019). Coupled electrophysiological, hemodynamic, and cerebrospinal fluid oscillations in human sleep. Science.
【2】Jerath, R., et al. (2006). The physiology of long pranayamic breathing: Neural respiratory elements may provide a mechanism that explains how slow deep breathing shifts the autonomic nervous system. Medical Hypotheses.
【3】Lagopoulos, J., et al. (2009). Increased Alpha Brain Waves During Meditation. The Journal of Alternative and Complementary Medicine.
【4】Lutz, A., et al. (2004). Long-term meditators self-induce high-amplitude gamma synchrony during mental practice. Proceedings of the National Academy of Sciences.
