Why Do We Dream? Physiology Of Dreams

What happens when we sleep?

Why do we sleep? The answer is not as simple as it seems. We sleep so that our body can rest, we think at first. However, science has not been able to prove concretely that sleep is necessary for physical recuperation of the body. Experiments performed on rats have proven that when deprived of sleep, these animals die.

But human nature is not as simple as that of rats. Everyone knows people who barely sleep. The most extreme case, published in some scientific magazines, is that of a man who claims not to have slept since contracting a serious illness. In a similar vein, some individuals with a highly developed spirituality are able to remain conscious all night. We’re not referring to a student during exam time drinking coffee or taking stimulants to stay awake more than twenty-four hours straight. We’re talking about people who can achieve advanced levels of relaxation through deep meditation.

It is known that anxiety and lack of concentration increase considerably after a night or two without sleep. One theory related to sleep affirms that we sleep to conserve energy. However, another suggests that we rest to conserve our food stores, since when we lose consciousness, we repress the hunger mechanism.

How much do we sleep?

Sleep at different ages

In the course of his life, a person has, on average, 300,000 dreams. As we age, both the time we spend sleeping and the time we spend dreaming decrease gradually.

Newborns sleep almost all day, alternating hours of sleep with short spells of wakefulness. By one year of age, they sleep fewer sessions but for longer in total: they have cycles of 90 minutes of sleep followed by another 90 minutes of waking time. Gradually, the child will sleep more at night and less during the day. By 9 years of age, most need between 9 and 12 hours of sleep a day.

The average for an adult is between 7 and 8.5 hours. But after age 70, we return to the sleep phases of childhood and sleep fewer hours continuously.

There are arguments that even claim we have slept since ancient times in order to appear a less tasty snack for nocturnal predators (when we sleep, our body looks like a corpse).

There are theories to suit everyone, but we shouldn’t forget the fundamental: for almost all of us, sleeping is a relaxing and pleasant experience that lasts between six and eight hours each night, an experience that is utterly necessary to “recharge the batteries” of our bodies.

It’s no coincidence that we choose nighttime to sleep. In the darkness our vision is reduced, the world becomes strange, and as a result, our imagination runs wild. Our minds remain occupied with images (that is, dreams). At night, our eyes don’t work, but we have a need to create images. If for some reason we are deprived of sleep, the following nights our dream production increases, since we spend more time in the REM phase (the period of sleep when oneiric thoughts are most active). Therefore it seems evident that we need dreams to live.

Some ancient civilizations believed that dreaming served, more than anything, to be able to dream. They were convinced that oneiric activity wasn’t the result of sleeping, but rather the reason for it. Some scientists, however, don’t share the theories of our ancestors when it comes to the reason behind our dreams.

There is a scientific school of thought that asserts that oneiric thoughts are simply a neurophysiological activity that comes with sleep. According to this theory, when we sleep we generate spontaneous signals that stimulate the sensory channels in the mind. The brain transforms these signals into visual images and induces the dreamer to believe that he is living real experiences.

Up to that point, perfect. But, why do dreams have such an interesting narrative? Why do they so often express metaphoric language? Why do they narrate stories that directly affect us? There is no concrete or scientific answer to these questions.

Percentages of REM sleep

Cold-blooded animals never dream; the cold temperatures at night cause them to hibernate and all their vital functions, including the brain, slow down. Only when the sun comes out or the temperature rises to an acceptable level do they recuperate all vital functions. The only cold-blooded animal that has shown signs of dreaming is the chameleon.

On the other hand, we know all warm-blooded animals dream, since REM-phase activity has been detected in all of them. Birds dream only about 0.5% of the time they spend asleep, while humans dream up to 20% of the time. There are exceptional cases, such as that of the Australian platypus, that never dream.

Other theories suggest that dreams serve to eliminate unnecessary facts from memory, since we can’t store everything that happens every day. According to this thesis, at night we erase the “archives” we don’t need, just like a computer. The sleeping mind tests the process of erasing in the form of dreams, which would explain why they’re so difficult to remember. There are obvious limitations to this theory if you keep in mind that, occasionally, oneiric thoughts work creatively (they go beyond the information that we give them). These don’t have much to do with the merely “hygienic” function that the aforementioned scientific community claims. Often, dreams don’t eliminate the useless leftovers of daily experiences. Quite the opposite: they give them a surprising new shape, so when we wake up, we can reflect more deeply on their meaning.

The phases of sleep

Even though we don’t realize it, when we sleep at night we pass through four different phases of sleep. Each phase is distinguished by the deepness of sleep. That is, when we are in phase 1, it is a fairly light sleep; during phase 4, we reach maximum intensity.

When we go to sleep, we enter a period in which we gradually pull away from the exterior world. Little by little, our sleep deepens until finally (phase 4) our breathing slows and becomes regular, our cardiac rhythm slows down, and our body temperature decreases. Therefore the body’s metabolism also reduces its activity.

More or less an hour after falling asleep, your body has already gone through the four phases. At this point you begin to go back through the levels until you return to phase 1. This brings along an increase in respiratory and cardiac rhythm. Parallel to this, brain waves once again start to register an activity close to that of consciousness. You are therefore in a moment of transition, demonstrated by the fact that at this point the body tends to change position.

All signs indicate that any noise might wake us. But that’s not the case: since your muscle tone has been reduced, this is actually the moment when it’s most difficult to regain consciousness. At the same time, your eyes begin to move behind your eyelids (up and down and side to side). This ocular phenomenon, which anyone can observe easily, is known as the REM phases, which stands for “rapid eye movement.”

Certain areas of the brain are associated with different functions and human skills, translating external sensory stimuli into a well-organized picture of the world. In dreams, those same stimuli produce different reactions. If a sleeping person hears a sound or touches something repulsive, those stimuli will probably be integrated into their dream before they wake up.

The REM phase

The REM phase is particularly important for those interested in dreams. All studies indicate that during this brief spell (from five to ten minutes) we typically experience the most intense oneiric activity. Some of these studies, done in a sleep laboratory, have observed that eight out of ten individuals relate very vivid dreams when woken up right at the end of the REM phase. These periods alternate at night with what we could call non-REM phases, that is, periods when no ocular movement is registered.

How many times do we reach a REM stage at night? It is estimated that each cycle is repeated four to seven times. As the hours pass, each phase gets longer. This way, the final REM stage might last twenty to forty minutes. On average, an adult enjoys an hour and a half of REM sleep each night, although for older individuals it may be less than an hour and a quarter. Babies, on the other hand, remain in the REM phase for 60 percent of the time they spend asleep.

In any case, let’s make this clear: not all dreams are produced during this period. It has also been demonstrated that humans generate images in other stages. However, these are dreams of a different quality, since during the non-REM phases, our oneiric activity tends to generate only undefined thoughts, vague sensations, etc. Nothing close to the emotional content that characterizes dreams produced in the REM phase.

The oneiric images produced in the most intense phase (REM) are more difficult to remember. One method to remember them consists of waking up just after each REM phase.

As we’ve commented already, those who wish to read their dreams have to first do the work of remembering them. If we want this work to be 100 percent effective, we can use a method that, although uncomfortable, almost never fails: wake up just after every REM phase. If you want to try this method, set your alarm (without music or radio) to go off four, five, six, or seven and a half hours after falling asleep. You can be sure that if you wake up just after one of the REM phases you go through each night, you will enjoy vivid memories.

This is the process used in sleep laboratories, where oneiric activity is studied through encephalographic registry of electrical brain activity.

The people in the study—who are volunteers—sleep connected to machines that register their physiological reactions (brain waves, cardiac rhythm, blood pressure, muscle activity, eye movement, etc).

At certain points during the night, these reactions indicate that, if you wake them, they will be able to tell you what they dreamed. This is because the phase that produces the most intense dreams (REM) is characterized by a physical reaction easily observed: the rapid movement of the eyes of the dreamer.

With this method, sleep laboratories can collect proof of precisely

when subjects are dreaming. And given that oneiric images are difficult to remember, the lab techniques have been a great advance in dream research. Some experts assert that thanks to the scientific advances of the second half of the twentieth century, we have learned more about sleep processes in the last fifty years than in all the history of humanity.

What do we dream?

A wide study done in France on the subject of dreams produced these results:

• Relationships with partners (18%)
• Home, especially that of our childhood (15%) -Aggressors, thieves, being chased, etc. (10%)
• Missing the train; embarrassing baggage (8%) -Water, wells, tunnels; traffic accidents (6%) -Forgotten children or babies (5%)
• Snakes, fires, stairs (5%)
• Negative animals: spiders, cockroaches, rats, etc. (4%) -Clothing or lack of clothing; nakedness (3%)
• Losing teeth or other alarming situations (2%)

Hypnagogic images: between waking and sleep

As we’ve seen, throughout the night our sleep is divided into four distinct phases. But what happens just before we sink into the first phase? Are we still awake? Not exactly. In the moments when our mind decides between wakefulness and sleep, we begin to lose contact with the world around us, without the characteristic physiological changes of sleep.

This intermediate point has been called the “hypnagogic state” by psychologists. This is a period when, despite the fact that we’re not asleep, our brains generate images that can sometimes be very beautiful. In some ways, these images rival those found in our dreams.

Hypnagogic images of great visual beauty evaporate like bubbles when we wake up and are barely remembered.

However, the hypnagogic state cannot be considered a truly oneiric state. Among other reasons, the scenes produced in this phase are unrelated to the episodes with a more or less coherent plot that characterize dreams.

In the hypnagogic state we produce unrelated images that hardly connect to each other and that, unlike dreams, are not linked to our daily experiences. This phenomenon occurs not only before sleeping but also in the moments before waking up, when we are not yet conscious enough to be aware of them.

Sometimes, before falling asleep we also experience a curious sensation of floating or flying, or we may see very sharp scenes, with a clarity comparable to that of real visual experiences. These types of images, like dreams, evaporate like bubbles when we wake up and we barely remember them, which is a shame because their beauty slips from our minds. In any case, unlike oneiric thoughts, the hypnagogic state is little use for understanding the messages our subconscious wants to send us, and we should value it more for its beauty than its transcendental content.

Salvador Dali, painter of dreams.

To remember them you must not lose consciousness during the apparition. That is, you must observe the process of the hypnagogic state without falling asleep. It seems simple but it is not, because you must submerge yourself in sleep while the mind remains aware of the events happening in its interior. With a little luck, we can see some of the marvelous “paintings” of our private museum.

The surrealist artists of the 20s and 30s knew all about this. This is how Salvador Dali, fervent lover of hypnagogic scenes, turned to what is known as “the monk’s sleep.” He went to bed with a large iron key in his hand. With the first dream, the key would fall to the floor and he would wake up suddenly. In his mind he recorded the hypnagogic images he would later transfer to the canvas in his masterful style.

The seven “chakras,” or centers of subtle energy in the ayurvedic hindu medicine (1).
The nadis according to Tibetan tradition (2).
The meridians of traditional Chinese medicine (3).

If you have difficulty retaining the hypnagogic state, try centering your attention on a concrete point. For example the “third eye” of the yogis (that is, between your eyes), in the area of the heart, or in the top of the head. These three positions are, according to the philosophy of yoga, the centers of subtle rather than physical energy in the human body. You need a place to direct the mind. Another trick to hold attention without effort is to think abstractly about the name of the object you wish to see. This doesn’t mean you have to “create” the images; you just have to induce its appearance during the hypnagogic state. Entering through meditation is also very useful and beneficial.

Sometimes, the hypnagogic scenes are not as pleasant as we would like, but we must confront them in order to strengthen our ability for self-control. If they persist, try following the previous advice. Think abstractly about the name of what you want to see, resisting the temptation to construct it in a certain way from the conscious mind.

The main advantage of the hypnagogic state is that it brings us progressively closer to our deep Self . . . and all that helps to understand and better benefit from dreams.

The same subject can have very different meanings depending on the circumstances and personal situation of the dreamer.