Why do we dream?

Science

24 maart 2020
Article
Auteur(s): Philip Lepoutre
Do our dreams have any meaning or any purpose?

by Philip Lepoutre

Science Editor

A study conducted by Kamitani Lab from Kyoto University which used artificial intelligence on the human brain is our latest attempt to understand the nature of our dreams. In this study a program recorded the brain patterns of people while they were awake to identify what they correspond to (e.g. certain parts of the brain become activated when shown a telephone) and then reverse engineered the brain patterns recorded while the test subjects were asleep. When the subjects awoke, many of their descriptions matched the readings of the computer.

Dream Caused by the Flight of a Bee Around a Pomegranate a Second Before Awakening by Salvador Dalí, 1944

In this Salvador Dalí painting, a woman is woken by a passing bee, and her brain makes up an elaborate dream to explain the buzzing sound she hears as well as the feeling of being stung: roaring tigers and the stab of a bayonet. Dalí really loved dreams, and this very painting really reflected a common view of dreams back in 1944. 

Before we fall asleep, our brains are a collection of chattering neurons, which produce chaotic Electromagnetic Waves. As we fall asleep and lose consciousness, we enter the Slow-Wave sleep, characterised by a moderate Electromagnetic Wave frequency (Bellesi et al 2014). During that period, the activity of the brain decreases dramatically. But one hour and a half later, something odd happens: the brain roars back to life and the brain waves look exactly like as if we were still awake – neurons are talking to each other, sending out signals to move and speak and jump - this stage is called the REM sleep. However, a part of our brain called the Pons – present in the Brain Stem– stops us from moving around, and our bodies are temporarily paralyzed except for our eyes, which can be seen to move giving rise to the the name REM sleep (Rapid Eye Movement sleep).

(A) An Electroencephalogram (EEG) displaying changes in brainwave activity of an average human during different stages of consciousness. Image from Lumen Learning. (B) Diagram displaying the position of the Pons with respect to other parts of the brain stem. Image by Patrick J. Lynch, medical illustrator, and C. Carl Jaffe, MD, cardiologist.   

In some cases, the small part of the brain know as the Pons malfunctions and leads to pretty scary results. An example of this is Mike Birbiglia, who acts out his dreams and thus sleeps in a sleeping bag up to his neck and wears mittens so he cannot open the sleeping bag. However, for most people, only the eyes act out their dreams. If you’re dreaming of a tennis game, your eyes will move back and forth with the imaginary ball. This very fact confirmed that we experience our dreams during sleep, and that we do not make up our dreams in the moment of awakening. 

During sleep, one of the major parts of the brain that remains turned off is the logical judgment filter, the Prefrontal Cortex.

Having that logical filter turned off during sleep is probably why some of our dreams are so bizarre and make no sense. In contrast, our entire emotional part lights up (Amygdala & Hippocampus), and they are so active that they surpass even the levels of activity seen during the day while awake. Hence, during REM Sleep, the emotional part of our brain is very active while the reasoning one is barely present. According to  verywellmind.com, we spend around one 5th of our nights dreaming, however most of the dreams are forgotten.

Why do we forget our dreams? It turns out that during our sleep we have much lower levels of Norepinephrine, a chemical messenger that makes us feel awake and alert. And in the brain. It causes it to feel memories. The levels of another chemical called serotonin dramatically decrease as well.

Spontaneous discharge (firing rate) of norepinephrine containing locus coeruleus neurons in the brains of rats during their sleep-waking cycle measured by Aston-Jones et al, 1981. Image from Pearson Education, Inc.

In 1899, two books were published that were proven to be very important towards the scientific explanation of dreams. The author was Santiago Ramon y Cajal, known as the father of modern neuroscience. His books spelled out the idea that neurons were the basic units of the nervous system. Experiments by other scientists showed that these neurons communicate by using electrical signals, and this gave them the idea to apply small electrical signals on the brain to try creating images within the human mind. According to a Vox article, in the 1930s, Wilder Penfield made some experiments where he zapped the brain of his human test subjects and recorded their response to it. The result was shocking: “I hear voices. It is late at night, around the carnival somewhere — some sort of traveling circus. I just saw lots of big wagons that they use to haul animals in” said one test subject; another said “Now I see them, they’re laughing”; and another “I hear children’s voices”; and another “I see the whole thing. A guy coming through the fence at a baseball game”.

Some scientists still believe that dreams are just a series of random electrical impulses in our brains.

However, the Interpretation of Dreams by the father of psychoanalysis, Sigmund Freud, claimed that dreams were so much more. According to the book, dreams are representations of our innermost desires. One of Freud’s earliest supporters, Carl Jung, also believed that dreams are messages from the subconscious. He thought that dreams contained characters that depicted aspects of our inner lives, ranging from Anxiety, to Purity and even Wisdom.

“Dreams are often most profound when they seem the most crazy.”

Sigmund Freud, Austrian neurologist and founder of psychoanalysis

Since then, scientists have analysed the content of hundreds of thousands of dreams and have noticed some patterns. Dreams of being chased, of falling and of having sex are among the most common. Some of these and their explanations have been summarized by beliefnet.com in an article entitled “What these common dreams are telling you”.  About 1 in 5 people have dreamed of their teeth falling out. Men are more likely to dream about other men, while women dream about both sexes quite equally (Hall et al, 1966). Children are more likely to dream about animals (Bernstein, 1985), and only 5% of dreams are set in locations the dreamer doesn’t recognise. Some people argue that what we dream about doesn’t come from our daily lives, but a study by Stickgold et al says otherwise. He recruited a number of subjects to play Tetris for 3-4 hours a day, and lo and behold, Tetris-like structures started appearing in their brains. He also studied people with memory disorders, who couldn’t even remember what Tetris was after playing it, but some elements still managed to make their way into their dreams.

So, what do we know about dreams? Nothing and everything at the same time, who knows what scientists might discover about them in the near future.

Until next time and keep dreaming!