Sleeping, originally a very natural thing, is as natural as breathing air, is a relaxing and happy thing. But in reality, many of us have experienced insomnia? Some people say that insomnia is an inevitable encounter on the road of life, because 300 million Chinese have sleep disorders. How can I get a good night's sleep? Become an important issue.
Brain waves during sleep
First, sleep and the brain
1. Sleep center. Sleep is controlled by the sleep center. The sleep center is located at the caudal end of the brainstem and the hypothalamus, and the conduction impulses emitted are used in the cerebral cortex and are constrained by the action of the ascending system of the brainstem reticular structure that controls the arousal state, thereby regulating the mutual conversion of sleep and wakefulness.
The narrow sleep center is usually located in the hypothalamus, which is part of the diencephalon and is located deeper, deep in the brain. The preoptic area of the hypothalamus is closely related to sleep, and if this area is damaged, patients will have severe insomnia. The posterior part of the hypothalamus is associated with wakefulness, and patients experience hypersleep and reduced waking time after damage.
It is often said that the human body clock is located in the hypothalamus. The hypothalamus is part of the diencephalon, located deep in the cerebral hemispheres, between the midbrain and both cerebral hemispheres, which is the highest center under the autonomic cortex.
In addition to the hypothalamus, the ascending reticular activation system is strongly associated with arousal and sleep. This system is mainly located in the thalamus, that is, the dorsal thalamus and midbrain, after the lesion of this part, patients will have excessive drowsiness, not waking up, and even sleep reversal, black and white reversal, and coma in severe cases. Therefore, the sleep center in a broad sense also includes the ascending reticular activation system of the midbrain and thalamus. The "arousal response" of the brain part of the reticular activation system is very different from the thalamus part of the reticular activation system. The former activates almost the "whole brain", while the latter is just a transit site for the former.
Sleep cycles
2. Sleep cycle. There are two states of sleep, which are non-REM sleep NREM (slow wave) and REM (fast wave). (1) Slow-wave sleep: NREM stage, divided into I, II., III., IV 4 periods; (2) Fast wave sleep or heterogeneous sleep or rapid eye movement, that is, REM sleep. The sleep process is composed of the alternation of these two states of different nature. In the 8-hour sleep of normal people, the two kinds of sleep should be cycled 3~6 times. NREM sleep is divided into four stages: sleep, light sleep, medium sleep and deep sleep.
REM sleep is closely related to the appearance of dreams. During REM sleep, people often dream, which are often very realistic and sometimes absurd. Dreams are expressions of people's psychological and emotional experiences. Dreams are actually a normal expression of people.
Non-REM sleep (NREM stage) exhibits Sharp-wave ripples, Cortical slow oscillations, δ waves and Spindles. REM sleep is mainly based on theta wave oscillation. NREM stages are related to dreams, relatively simple, ephemeral and realistic, and are usually related to our experiences, thoughts, and memories during the day.
The NREM phase consists of three distinct phases, N1, N2, and N3. Among them, the N1 and N2 stages are considered to be light sleep stages. In the N1 phase, people are often half-asleep, confused, breathing and heart rate become slower, and eye movements are reduced. This phase usually lasts for a short time, only a few minutes. In the N2 phase, breathing and heart rate slow further, muscles relax, and brain waves begin to become more regular. This stage is the stage when most people sleep the longest, usually lasting 40 minutes to about 1 hour and a half. Light sleep usually refers to the N1 and N2 stages of the sleep process.
Light sleep - the brain is extremely active, even beyond the time of wakefulness, when the brain is actively processing short-term memory, especially emotional memory, removing negative feelings, softening strong emotions, and helping to maintain emotional balance and physical health.
Deep sleep. Deep sleep usually occurs in the first half of the sleep cycle, it is a very important restorative sleep stage, also known as the third stage of NREM (Non-Rapid Eye Movement) sleep. During the deep sleep phase, both the body and brain are in a state of deep relaxation, the body's cells and tissues are repaired and restored, and protein synthesis and growth hormone secretion are increased. This phase of sleep is generally considered to be the most beneficial for the body's recovery and repair. Deep sleep – The brain is putting important information into long-term memory while the body recovers.
3. Chemicals and neurochemical transmitters in sleep. Sleep is an active rather than passive inhibitory process. A large number of studies have proved that the control site of slow-wave sleep is the middle suture nucleus of the brainstem, the control site of heterogeneous sleep is the middle and tail of the blue spot of the pons, and the control part of arousal is related to the anterior part of the blue spot and the midbrain reticular structure. Both sleep and wakefulness are instinctive. It is also a reflection of the biological clock. Norepinephrine (NE) and serotonin (5-HT) are a pair of mediators that determine sleep and wakefulness. When the NE content in the brain remains unchanged or increases, reducing the content of 5-HT can cause insomnia; When the amount of 5-HT in the brain is normal or increased, reducing the NE content causes drowsiness. Serotonin is necessary for sleep, and blue spots are the main secretory tissue.
4. Circadian rhythm. The cycle of the biorhythm is close to the Earth's rotation cycle, called the "24-hour circadian rhythm". The nature of sleep and wakefulness is first limited by the "24-hour circadian rhythm" close to the Earth's rotation cycle, and the latter restricts the former by acting on the brain network structure and other parts through the pineal cone system. Modern research shows that the reticular activation system is the basic site for regulating sleep and wakefulness. It begins in the lower part of the brainstem, extends to the midbrain, and includes the midline and reticular nucleus of the inner medullary plate of the thalamus. Electrical stimulation of the midbrain part of the reticular activation system (including the pontons and the reticular structures in the upper medulla oblongata) can awaken sleeping animals instantly. The circadian clock is in a different position. In mammals, including humans, the circadian clock resides in the "suprachiasmatic nucleus" neural tissue of the hypothalamus.
Suprachiasmatic nucleus: Located above the optic nerve intersection of the two eyes, this area contains about 10,000 neurons that are particularly sensitive to light, which are your biological clock, always feeling the circadian rhythm from the mysterious universe.
Pineal gland: Only the size of a grain of rice is located at the top of the upper part of the third ventricle of the brain, between the corpus callosum and the upper thalamus, and it has a very important function is to produce a sleep-inducing hormone called "melatonin" to make you lethargic. The drug melatonin is a synthetic melatonin that can be used to treat a variety of sleep disorders, such as insomnia, jet lag, night shift work, etc.
Biological clock. In addition to affecting the amount of sleep in the body, the brain also controls people's sleep time. How does the body know when to fall asleep and when to wake up? Cells in the brain's suprachiasmatic nucleus are clock-aware and monitor sleep and wakefulness cycles. The pineal gland produces melatonin. When dusk comes, the sky begins to darken and melatonin begins to be secreted in the body. Suprachiasmatic nuclear cells control not only the time each person falls asleep or wakes up, but also the functioning of many other systems in the body. In fact, most systems in the body operate differently throughout the 24-hour period. With the secretion of a variety of hormones, blood pressure and heart rate will also change.
Sleep EEG
The body's circadian clock is controlled by an area called the Suprachiasmatic nucleus (SCN). The blue spot nucleus is located in the hypothalamus, above the intersection with the optic nerve, so it can be affected by visual signals, especially blue light signals. Blue light helps regulate a person's biological clock, which promotes sleep. Studies have shown that when we are exposed to blue light, a light-sensitive protein in the retina called melanopsin is activated, producing signals that are transmitted through nerves to the blue spot. After receiving these signals, the blue spot nucleus promotes the secretion of melatonin in the body, thereby regulating the body's biological clock. The role and effects of blue light are relatively complex, and different people and different sleep problems may have different effects.
Second, the function of sleep
1. Sleep removes metabolic waste.
There is a unique "garbage disposal system" within the brain - this system cleans even faster than the well-known body lymphatic system, which is named "lymphoid system".
It works by the fact that cerebrospinal fluid flows along the periarterial space into the brain tissue, constantly exchanges with the intercerebral tissue, and carries the metabolic waste of the intercellular fluid to the perivenous space, which is then expelled outside the brain. Almost all of this work is done during sleep. The basic role of sleep, removing toxic metabolites from the brain. When people sleep, the system that removes waste products from the brain is most active.
The β amyloid protein produced in the brain can β accumulate in cells to become pathogenic plaques, which has been linked to the occurrence of Alzheimer's disease. That is, long-term lack of sleep and low sleep quality will lead to the accumulation of garbage in the brain and increase the chance of Alzheimer's disease! Conversely, good, adequate and high-quality sleep can reduce the occurrence of senile dementia.
REM与NON REM
2. Sleep and memory
Sleep plays an undoubted role in memory consolidation. And in recent years, another theory has emerged - "synaptic homeostasis hypothesis" (SHY). Synapses are the connecting structures between neurons, and when we form new memories, the associated synaptic connections are strengthened. Simply put, when we are awake, due to the continuous generation of new memories, the need for synaptic connections to be continuously strengthened, while energy consumption continues to increase, so the brain will not be able to eat, and then the memory storage space shows insufficient margin, new memories can not enter. This problem is solved during sleep, and the brain weakens and balances those synapses to free up memory space to achieve sustainable development of memory. Slow waves are very important for memory integration.
Slow electrical oscillations (or "slow waves") of deep non-REM sleep promote memory integration. Slow waves, resonance of cerebrospinal fluid, electrical oscillation. Electrical stimulation is used to influence how brain waves ultimately treat encephalopathy, as well as to assess changes in CSF as diagnostic markers of the disease.
Slow-wave sleep can help us remember. So sleep helps the brain organize and review what it learned during the day. Oscillatory coupling of the three components of slow-wave sleep is most commonly found in the hippocampus. The hippocampus is very important for us to form new long-term memories. When we are in slow-wave sleep, the hippocampus will "replay in the form of sharp ripples" in the pattern of remembering things when you are awake, and transmit the reactivated hippocampal memory information to the neocortex, thereby promoting the synaptic consolidation process of neocortical network characterization and reorganization. Sleep "reshapes" hippocampal synapses, making room for the next day to study and children who take more naps do better. We can use this slow-wave sleep to aid memory. Therefore, it can be most efficient to strengthen the memory of something before sleep, and then it can connect learning content with slow-wave sleep.
Sleep is garbage removal
3. How to improve sleep?
Sleep is actually very simple, keep a simple mood, maintain good, simple habits, naturally you will have a good night's sleep. Here are a few tips to keep in mind.
1. Maintain 6-9 hours of moderate sleep; Rhythm is important; Routines of life; (Corresponds to sleep rhythm, adapts to the biological clock in the brain)
2. Relax and don't be nervous; Forgetting homework or work that you haven't started before you start and reducing anxiety levels (reducing stress helps balance sleep hormones, NE and 5-HT);
3. Create a quiet sleeping environment; Do not wake up when you are asleep; Reduce light interference; Blue light helps sleep;
4. Induce sleep through meditation, yoga, listening to soothing music, etc. (use the rhythm of music to tune brain waves so that they enter NREM as soon as possible);
5. Appropriate exercise can also promote sleep (exercise secretes endorphins and dopamine, etc., these chemicals can promote the body's relaxation and sleep, regulate the HPA axis, sympathetic nervous system and brainstem-reticular structure and other brain regions); Pharmacotonic (melatonin);
6. Avoid strenuous exercise and caffeine intake before going to bed; Avoid overexcitability (excitement alters the balance of sleep hormones).
-----------------------------------
About the author: Lu Wangsheng
Associate Chief Physician, MD
Chief medical expert of Qianglian Zhichuang (Beijing) Technology Co., Ltd
Deputy Chief Physician of Department of Neurosurgery, Beijing Tiantan Puhua Hospital