The Secret World of Sleep
Sleep often gives people a sense of comfort and rejuvenation, but for the patient, sleep is not at all peaceful and comfortable. A clinical neurologist Guy Leschziner said that a patient realized that he had used a motorcycle to go for a ride while sleeping until the landlord stopped her and asked her where she was going. The other would walk around while asleep, and make the dream movements-his wife was terrified. Other patients still suffer from lack of sleep, insomnia, and night terrors.
In his new book “Nocturnal Brain: Nightmares, Neuroscience, and The Secret World of Sleep,” Dr. Leschziner introduced and explained how these cases have inspired the fast-growing field of sleep research.
He said: “These cases are very interesting in two respects. First, the stories composed of the patient’s personal experience are extremely dramatic; second, through these extreme cases, we can glimpse the situation of normal people, that is by observing these Patients and finding out the cause of their brain abnormalities can deepen our understanding of how the brain regulates sleep.”
What contributes to a good night’s sleep? What happens in the brain when dreaming? What health problems will sleep disorders reveal?
Regarding these questions, The Verge interviewed Dr. Leschziner. The interview draft has been slightly compressed and deleted for clarity.
You have written a lot about the patients you receive and their abnormal sleep, but I want to start this interview from the opposite perspective: What is normal high-quality sleep?
Sleep is not only an objective experience but also a subjective experience. From an objective point of view, adequate and solid sleep can be said to be quality sleep.
For most people, 7 to 8 hours of sleep is ideal. But everyone’s subjective experience of sleep is different. Some people wake up many times at night, and they can still be refreshed during the day. On the other hand, other people, no matter how you look at the night, are enough and practical sleep, but they feel abnormally tired and sleepy during the day. Therefore, the subjective experience of sleep is not the same as the objective appearance that sleep presents to us.
If you go to bed and get up at the same time every day, are full of energy during the day, and fall asleep at a fixed time, then you probably have enough sleep.
Why do we need sleep?
In a brand new laboratory in Japan, an international scientific research team is exploring the mystery of sleep.
From the perspective of a sleep researcher, what do you think of the prevalence of sleep monitoring equipment?
I don’t think there is an inherent error in monitoring sleep, but you’d better ask yourself, Why do I want to monitor my sleep? If you monitor sleep because you feel that you don’t have enough sleep, it’s not practical to monitor equipment. Let me tell you this.
But I think the hidden danger is: if people monitor their sleep because of insomnia, or feel severe lack of sleep despite being asleep for a long time, and feel anxious because of not necessarily accurate monitoring data, this will strengthen their misunderstanding of sleep Therefore, it enhances sleep anxiety and worsens insomnia and other problems.
Some of your patients, such as John, claim to have experienced unusually vivid dreams and start to dance their bodies in their sleep. Is there any connection between their body movements and the things experienced in their dreams?
Under normal circumstances, when we dream, our body is completely paralyzed. Only the muscles that allow the eyes to move to retain some athletic ability-this is where the term “rapid eye movement sleep” (REM) comes from. Also, some muscles maintain breathing. Obviously, stopping breathing (during sleep) from an evolutionary perspective is not a good idea.
Therefore, there is a mechanism in the brain that makes the body paralyzed when REM sleep starts. But John’s mechanism went wrong, so when he started dreaming, it can be said that without a paralyzed body, he implemented the actions in his dreams.
Unexpectedly, dreams play a very important role in your book about sleep. Why do we dream? How much do we know about this now?
We know that the stage of sleep that is most related to dreaming (REM sleep) changes with the course of life. Even before we are born, we are in REM sleep for one-third of every 24-hour cycle. But this also begs the question: What are we dreaming about in the mother’s womb? What is the role of dream experience? One possible explanation is that dreaming, or more specifically REM sleep, has different effects at different stages of life.
In the early stages of development, when embryos or newborns, the role of dreams may be to promote the development of specific neural pathways related to consciousness. In the days to come, dreaming is not only vital to promoting learning, but it may also play a big role in regulating emotions.
Now, if you think of the brain as some kind of supercomputer, what it does is to receive a huge amount of information and interpret it based on its own experience of the world.
Essentially, our brain has written a predictive model, and we can import what we are experiencing into this model and draw predictions from it. But we are getting new information every moment when we are awake, all of which act on the picture of the world around us. This means that our world model must be constantly fine-tuned.
Maybe we never live in the present, but always look forward to the coming future
A controversial theory believes that brain functions such as perception, motor control, and memory are all realized by the brain by stimulating the future and comparing it with the experience of the moment.
This may be a dream, it is the refinement of our understanding of the world. I think this explains why we both dream of the distant past and the experience of the day. It is the melting and reinterpretation of all our experiences in the world model we have established.
A recurring theme in your book is that some sleep disorders may indicate more serious health problems. Can you talk about it?
We are now beginning to realize that sleep is important for the regulation of almost all physiological activities in our bodies. More and more studies are starting to investigate whether sleep disruption, sleep deprivation, or other physical conditions, such as sleep apnea, can cause symptoms such as dementia.
We have learned that poor sleep quality and sleep apnea are associated with cognitive decline, and more and more evidence suggests that they may really be risk factors for dementia. Although we have not yet reached a definitive conclusion on this, this is an exciting area. Because if we can prove that sleep apnea does greatly increase the risk of dementia, then this risk factor becomes adjustable.
The reason why sleep is so critical to dementia may be related to a series of channels in the brain, which are called the glymphatic system, through which the brain removes toxins and its own metabolites. During deep sleep, these ducts expand by approximately 60%. In other words, when you fall asleep, your brain can wash away these harmful substances more effectively.
Your brain will automatically erase the memory, after all, too much garbage is not worth it.
Many researchers today believe that forgetting is necessary because the meaning of the brain’s memory mechanism is not to preserve information but to make better choices.
You talked about 60% expansion, which is really a big number, but how big are the pipelines we are discussing?
They can only be seen under a microscope. In fact, for so many years, we didn’t even know their existence, and only really discovered them in the last ten years.
It sounds like there is still a lot of research to be done!
The most interesting thing about sleep medicine is that we spend an average of 8 hours sleep every night, and we slept a third of our lives. However, we have always had little knowledge about sleep before, and it hasn’t gotten deeper until recent years. We have made tremendous progress in the past few decades. But there are still many questions waiting for us to explore.