Sleep and Dreams: REM Sleep

In 1953, Aserinsky of the University of Chicago observed by chance that his child, though sleeping with his eyes closed, would rapidly move his eyes every so often. After careful observation, he discovered that this eye movement occurred approximately four to five times throughout the night. Aserinsky and his teacher, Nathaniel Kleitman, continued to observe others and found that they all exhibited this phenomenon during sleep. Therefore, they named this period of rapid eye movement during sleep "Rapid Eye Movement Sleep" (REM sleep).

This discovery completely overturned the prevailing view of sleep at the time: "Sleep is the cessation of most brain activity." They found that the existence of REM sleep suggested that something becomes active during sleep. All terrestrial mammals studied exhibit REM sleep, while other periods of sleep during which the eyes do not move rapidly are called "non-rapid eye movement sleep." REM sleep and non-REM sleep have a regular alternation cycle.

"Rapid Eye Movement (REM) sleep" is a stage of sleep in animals during which the eyes move rapidly while the body muscles relax. REM sleep is also known as Paradoxical Sleep (PS) or Desynchronized Sleep because during this stage, the activity of neurons in the brain is the same as when awake, exhibiting rapid, low-voltage, desynchronized brain waves.

Clinical studies suggest that the electrochemical activity controlling REM sleep originates in the brainstem, characterized by high levels of the neurotransmitter ethylenecholine, accompanied by the near-complete disappearance of monoamine neurotransmitters, including histamine, serotonin, and norepinephrine. Many researchers have found that if people are awakened during REM sleep, most report dreaming, indicating a strong correlation between dreaming and the REM sleep stage.

During a night's sleep, a person typically progresses from wakefulness to sleep, then from light sleep to deep sleep, and finally from deep sleep to REM sleep. This completes one cycle, which takes approximately 90 to 120 minutes, and a person needs about four to five cycles per night. Previously, it was mistakenly believed that dreaming only occurred during REM sleep; however, advancements in technology and research methods have revealed that dreaming also occurs during other sleep stages besides REM.

The probability of dreaming when falling asleep is 30-401 seconds, during light sleep it's 70-75 seconds, during deep sleep it's 50 seconds, and during REM sleep it's 85-90 seconds. For a typical young adult, light sleep accounts for approximately 50-55 seconds of a night's sleep, deep sleep for approximately 20-25 seconds, and REM sleep for approximately 20-25 seconds.

I dream every night

Throughout the night, people experience alternating cycles of rapid eye movement (REM) sleep and non-rapid eye movement (NREM) sleep. Each cycle lasts approximately 90 to 120 minutes, and there are about 4 to 5 cycles per night, meaning there are 4 to 5 REM sleep stages.

Studies have found that if a person is awakened from REM sleep, there is an 80-90% chance they will report dreaming, indicating a strong correlation between REM sleep and dreaming. However, studies have also found that when a person is awakened from non-REM sleep, they may also report dreaming, with a rate ranging from 0-75%. Why are there such large differences in the rates obtained from different studies? This is because subtle differences in research methodologies lead to different results.

Regarding the claim that "I dream all night and feel more tired the more I sleep," from the perspective of the sleep cycle, to remember multiple dreams, one must wake up multiple times during sleep, and these wake-ups must occur either during or immediately after dreaming. In other words, remembering multiple dreams is due to constantly waking up during sleep, and this constant waking naturally leads to feelings of fatigue. Therefore, the actual situation is...It's not that having many dreams causes you to have poor sleep, but rather that having many dreams causes you to have poor sleep.！

The Study of Dreams

Most people think that whether or not they dream is a clear-cut matter, but in reality, it's not that simple. It's generally believed that whether or not one dreams depends primarily on whether they remember it, rather than whether they actually dreamed. This is because it's possible to dream but forget it, or not remember having dreamed upon waking. Each night, we experience about 4-5 REM (Rapid Eye Movement) sleep cycles, and there's an 80% chance of dreaming during each REM sleep cycle. Therefore, theoretically, we should have at least 3-4 dreams per night, not including dreams during non-REM sleep. However, most people only remember one dream, or even none at all, forgetting most of their dreams. This demonstrates the significant impact of memory on dream research.

So, under what circumstances are we most likely to remember our dreams? Generally speaking, we are most likely to remember our dreams when we are awakened during the dream or right after the dream ends. Therefore, if we have memories of a dream when we wake up in the morning, it is mostly the dream we had just before waking up, that is, the last dream we had during our entire sleep period.

Sigmund Freud, the founder of psychoanalysis, believed that dreams could reveal some hidden thoughts in people's hearts that cannot be expressed in a conscious state. Freud always believed that the interpretation of dreams was an important guide to understanding human mental activity, and dream analysis became an important foundation of his psychoanalytic theory.

How does Freud's theory of dreams differ from traditional dream interpretation? We can look at it from two aspects: (1) The nature of dreams; (2) The formation of dreams. Regarding the essence of dreams, Freud consistently maintained that all dreams are the fulfillment of wishes, but repressed wishes are fulfilled in a disguised form.

Traditional dream interpretation generally holds that dreams are the fulfillment of inner desires; for example, dreaming of drinking water is because of thirst, and dreaming of searching for a toilet is because of the need to urinate. However, Freud did not believe that dreams represent desires, but rather the fulfillment of desires. The reason people have dreams is to satisfy their desire to drink water in the dream, so as to avoid being awakened by the desire for thirst. Therefore, he called dreams "Guardians of Sleep."

But since dreams are the fulfillment of wishes, then logically all dreams should bring pleasure. However, in reality, many dreams not only fail to bring pleasure but also create anxiety and fear. Doesn't this contradict Freud's explanation?

Freud explained this situation by saying that people may have some thoughts and desires that they are unaware of, which urgently seek satisfaction at an unconscious level. However, these repressed desires may conflict with some conscious desires, or be incompatible with the individual's self or social values. These repressed desires may be satisfied in unconscious dreams, but the dreamer may not experience any pleasure in their conscious life outside the dream, thus causing anxiety after dreaming.

Looking at the formation of dreams, traditional dream interpretation explains the relationship between the content of dreams and reality using simple correlations. Therefore, some people believe that "dreams are always the opposite of reality," "what you think about during the day, you dream about at night," or "if you dream of dying, you will be reborn."

Freud believed that these methods of dream interpretation underestimated human psychological activity. He argued that any study of dreams must consider the distance between the dream content and the dream thought, and analyze how the dream thought is transformed into the dream content through a series of complex but principled steps, allowing the dreamer to experience it. In other words, the relationship between dreams and their meaning cannot be simply linked by a correlation, but is the result of a series of disguised and distorted transformations.

Freud discovered that his patients would react strongly to seemingly insignificant things for no apparent reason. For example, one female patient had an extreme fear of shopping alone, which she attributed to being mocked by male and female shop assistants for inappropriate clothing when she was young. However, after analysis, Freud discovered that her fear of shopping stemmed from witnessing male and female shop assistants flirting, which aroused desire within her, but which she later suppressed due to shame. Thus, at the conscious level, all that remained was the symptom of "fear of shopping"; the true cause—the awakening of sexual awareness—was "forgotten."

After observing a series of such cases, Freud came to the conclusion that one cannot regard a person's own narrative in a state of consciousness as reliable, but must go through the patient's free association and then conduct in-depth analysis in order to find the true meaning of these narratives.

Freud summarized the workings (processes) of dreams into six types:

Can dreams be controlled?

The outcome of a dream can indeed be altered through consciousness; this is known as lucid dreaming. The term "lucid dreaming" was first coined by the Dutch physician Frederick Van Eeden in 1913. In a lucid dream state, the dreamer can possess the thinking and memory abilities of their waking state. Some individuals can even make their dream experiences feel indistinguishable from the real world, yet remain aware that they are dreaming. Lucid dreamers can also remember most of the worlds and situations from their various lucid dreams. Lucid dreams differ from daydreams. In lucid dreams, the dreamer is fully conscious, aware that they are dreaming, and can plan and reason, freely altering the dream's plot to dictate its direction. Daydreams, on the other hand, involve the dreamer meditating or fantasizing while awake, without entering a sleep state. Instrumental examinations have confirmed that lucid dreams are indeed dreams, not merely waking-time dream images as some have suspected. However, lucid dreaming requires training.

This article references Dr. Yeh Shih-pin's "100 Questions about Sleep Problems - Dreaming" and Professor Ho Chun-jui's blog "Discussion on Issues - Dream Interpretation".