● Dreaming is usually related to REM sleep, and almost all REM sleep stages are full of dreams.
● People may dream during non-REM sleep, but this is different from REM sleep. Non-REM dreams tend to be scattered, and there will be more things similar to thinking; REM dreams have complex, lengthy and vivid hallucination characteristics.
"Dreams are a smooth way to understand the subconscious activities of the brain." Freud regarded this idea as a "once-in-a-lifetime" insight, which was recognized by academic circles in the 20th century. Looking around the world, on the sofas of countless psychoanalysts, clients describe their dreams in detail, convinced that they contain coded information of repressed desires. Dreams are no longer supernatural communication or divine intervention, but a window to spy on the hidden self.
Now our interpretation of dreams is completely different, and the technology used is far more advanced than simply writing down people's memories. In the sleep lab, researchers connected volunteers with electroencephalogram (EEG) and functional magnetic resonance imaging (fMRI) scanners, then woke them up from sleep and recorded what they saw in their dreams. Modern neuroscience has shown us some far-reaching revelations, and various discoveries have made us look at dreams from a brand-new perspective.
We now know that dreams, a specific form of consciousness, are crucial to shaping our behavior patterns. It will help us consolidate our memories, sort out all-inclusive experiences and keep our emotions under control.
The change pattern of electrical activity tells us that the sleep brain follows a cycle of about 90 minutes, and each cycle consists of five stages, namely, two shallow sleeps at the beginning, two deep sleeps thereafter, and then the rapid eye movement (REM) sleep stage. There is no specific brain activity pattern corresponding to dreaming, but as far as we know, all healthy people dream. Dreaming is usually associated with rapid eye movement sleep, which can happen at almost any time at this stage, but researchers have found that it can also happen in non-rapid eye movement sleep since the late 1960s, although the dreams of the two are different. Non-REM dreams tend to be scattered, and there are many similar things to think about, and they often lack the complexity, redundancy and distinctive hallucination characteristics of REM dreams.
Despite these differences, both dreams seem to reflect our sober life. Dreams often reflect recent experiences, especially when you fall asleep at night, and dreaming during non-REM is also common. For example, someone has been playing skiing video games just now and will dream that they are skiing. The relationship between waking experience and non-rapid eye movement sleep was also observed in brain scanning research. Pierre Ma Kai of the University of Liege, Belgium, investigated the late stage of non-rapid eye movement sleep, and found that the pattern of neural activity in brain replay of volunteers was the same as that caused by earlier waking experience. Many REM dreams also reflect the elements of the previous day's experience, but this connection is often more fragile, so that some people who have just played ski games may dream of rushing through the forest or falling off a cliff.
When we dream, we don't simply play back the events, but deal with them, consolidate our memory and integrate information for later use, thus playing a role in balancing the emotions in the body.
However, when we dream, we don't simply play back events, but process them in order to consolidate our memory and integrate information for future use. Robert Stegold of Harvard Medical School recently found that people who dream during non-rapid eye movement, as well as those who dream about the problems he asked them to solve, perform better in dealing with problems afterwards. Similarly, rapid eye movement sleep is also considered to be related to improving the ability to manipulate video games, complete visual cognitive tasks and extract meaning from a large amount of information.
"Obviously, when we sleep, the brain must do a lot of memory processing. When our brains organize these memories so seamlessly, it is certainly not just a coincidence that we are addicted to dreams. " Stegold said. He suspects that two kinds of dreams have different functions for memory, although what these functions are is still controversial. Stie Gleed thinks that non-REM dreaming may be more important for stabilizing and strengthening memory, while REM dreaming aims to reorganize the way the brain stores memories so that you can compare and integrate old and new experiences.
However, after examining the same evidence, Jan Born and Susan Tikelman of the University of Lü beck, Germany, came to the opposite conclusion: REM sleep supports the reinforcement of new memories, while non-REM sleep aims to consolidate higher-level memories. "It can be seen that we are still confused in understanding the influence of different sleep stages on memory." Stegold said.
What is not clear at present is how important dreams are in the formation of memory. Dreaming is certainly not the only time for us to consolidate our memories. For example, when we daydream, some areas of the brain called default networks become active. We now know that this network is related to memory processing, and most of the same areas of the brain are activated during active sleep. More importantly, daydreaming, like REM dreaming, can improve our ability to extract meaning from information and form creative insight.
Does this mean that we can process memories without sleeping? Stie Gleed doesn't think so. As he pointed out, whether daydreaming or dreaming at night, the way to play back new memories in the brain is different. Studies on mice have proved that when animals are awake, playback takes place in the opposite direction, and when they are asleep, playback becomes positive. No one is sure what this difference means for memory processing, but Volcker thinks it shows that daydreaming is not just a diluted version of sleep. Ma Kai felt the same way. "Different states of the brain may have different functions for memory. He said: "Memory consolidation may be organized through a series of cellular events, which need to occur in a series of ways. "It's just that some of them happen when you are awake, and some of them happen when you are asleep."
Even if dreaming is essential to memory, Volcker will not regard it as his main function. "More and more evidence shows that dreamy sleep plays a role in the emotional balance in the body: fundamentally, it perfectly rebalances the emotional compass on the biological level." He explained. It is a well-known fact that a short nap can completely change a bad-tempered 2-year-old child. Volcker has proved that adults have a similar tendency. He found that if a nap is accompanied by REM dreams, it is expected to alleviate the usual tendency of adults to become more nervous about angry or fearful faces in the rest of the day, and make people more willing to accept happy faces.
Volcker also found that sleep, especially rapid eye movement sleep, can strengthen negative emotional memory. It sounds like a bad thing, but if you can't remember the bad experience, you can't learn anything from it. In addition, both he and Stiglit believe that revisiting painful experiences will help to separate emotions from the experiences without the hormonal impulses accompanying actual events, so that they will be less painful as time goes by. Therefore, although dreams have strong emotional color, Volcker believes that they will gradually erode the emotional edge of memory. In this way, REM dreaming will act as an "analgesic ointment" for the brain. For people with post-traumatic stress disorder, this emotional stripping process seems to be out of order for some reason, which leads to traumatic memories coming to mind with all emotional details, resulting in extremely serious psychological consequences.
Like memory processing, REM and non-REM dreams may have different psychological effects. Patrick McNamara of Boston University found that people who wake up at different stages of sleep have different descriptions of their dreams. According to him, REM dreams involve more emotions, more aggression and more strangers, while non-REM dreams are more likely to involve friendly encounters. This leads him to speculate that non-REM dreaming will help us achieve friendly encounters, while REM dreaming will only make us relive various threats.
When you are asleep, the brain is actually reshaping itself. Dreams play a vital role in shaping you.
All this shows that we can't function normally without dreams, but it doesn't answer the puzzling question: What does a dream mean?
For some sleep researchers, the answer is simple and disappointing. Born believes that dreams themselves are meaningless, they are only incidental phenomena or side effects of brain activity during sleep, and it is this basic neural activity rather than actual dreams that is of decisive significance. Volcker finds it hard to agree with this. "I don't want to believe this, but I don't see much evidence to support the idea that dreams are meaningful." He said.
Researchers who reject the idea that dreams are irrelevant point to the work of Rosalyn Cartwright at Rush University in Chicago. In a series of long-term research work from 1960, she followed up the people who had experienced divorce, separation and bereavement. Those who often dream about these changes later show more mature resilience, which shows that their dreams are actually very helpful. "Cartwright's work provides some of the best evidence for the function of dreams," said Irene Walmesley of Harvard Medical School. She admits that there is no conclusive data to prove that dreaming is not an accidental phenomenon, but it also applies to waking up.
In fact, Walmesley's own research team also hinted that the form and content of dreams are related. She cooperated with Stegold to carry out research and found that non-rapid eye movement dreams can improve people's ability to solve problems. Their volunteers received 1 hour complex maze training, and then were allowed to take a 90-minute nap or stay awake. Volunteers who dream have greatly improved their behavioral ability, and the biggest gain is those who see the maze in their dreams. The contents of these dreams are obscure and seem unimportant. For example, a volunteer claimed to dream about the maze and the people at the border checkpoint-although there were neither people nor border checkpoints in the real mission, and then dreamed about the Bat Cave he visited several years ago. Stegold doesn't expect this to improve volunteers' ability to walk in the maze. "However, this person's ability to deal with difficult situations has been greatly improved."
He pointed out that all kinds of memories in dreams are archived together with other past experiences for future reference, and the content of dreams should also be consistent with this concept. "Dreams must be connected in a way that helps to improve memory function, not just an accidental phenomenon." He said, "I said this with almost fanaticism, which is the means I can resort to when there is no excellent data."
However, such evidence will appear one day. In the past, there was no objective means to record dreams, but this situation will change. Yasunari Kamiya of the Kyoto Brain Information Exchange Laboratory of the Japan Institute of International Telecommunications and Basic Technology (ATR) and his colleagues used functional magnetic resonance imaging scanning technology to create images reflected in the brains of volunteers when they were awake. Camia said that the research team has not conducted similar research on dreams, but it is feasible in theory. He added that it won't be like watching a movie, "but by using the latest technology, it is possible to predict what kind of dream a person is having."
Some people may think that this snooping and harassment of our dream world is destroying its magic, but researchers don't think so. When you are asleep, your brain reshapes itself by rebuilding and strengthening the connections between neurons. Therefore, although dreams will not reveal your inner secrets, they do play a vital role in shaping your mental outlook. "The mystery and miracle of dreams have not been touched by science," said Stie Gleed. "It just helps us to understand more thoroughly how incredible they really are."