Photo: Rodney Smith, Zoe on the Mattresses, New York, 2007
Is our sleep homogeneous? Does the dream have a “mother-in-law”? Why are nightmares so harmful and is it worth to be afraid of perfectionism? What dream is more ancient? Why is insomnia so harmful? What helps our brain to mature? We tried to answer all these questions in this article.
INDIANS AND GREEKS
The nature of sleep has worried people since ancient times. Gods and goddesses of sleep exist in almost all mythologies of the world. The Indian goddess of sleep Nidra Devi helped the warrior Lakshmana to stay awake for 14 years, who had vowed to protect his half-brother and sister. But the ancient Indians understood that sleep, like death, cannot be canceled. Therefore, his faithful wife had been sleeping instead of the hero for 14 years.
In Greek mythology, the god of sleep Hypnos and his brother Thanatos (Death), born of Night and Darkness, live in the underworld of Hades. Which is logical, so far as Hypnos takes from people half of their lives even during life.
The god of sleep dwells in a cave without light and sound, where day and night meet, and various hypnotic plants grow at the entrance to it. From Hypnos came the word “hypnosis”, although in fact the altered state of consciousness into which the hypnotist plunges a person into sleep, has nothing to do with sleep.
But Hypnos is most directly related to morphine, phobias and fantasies. The gods of dream Morpheus, Phobetor and Phantasos are the most prominent of the thousand children who, according to Ovid, were with Hypnos. Moreover, one of them, Morpheus, in the era of the European Middle Ages, managed to defeat his father in human memory and be associated with sleep alone.
NIGHTMARISH “MOTHER-IN-LAW” OF SLEEP
But for the Eastern Slavs, the Roman analogue of Hypnos, named Sonm, turned out to be much closer – almost the namesake of the Slavic Dream. The latter, according to some reconstructions, also had a wife – Sandman, as well as mother-in-law Mara, whose memory is preserved in the word “nightmare”. Etymologically nightmare is associated with the concept of an evil night demon in the form of a black mare.
As befits a devil or a mother-in-law from “male” jokes, Mara did not bring anything good to people, which was confirmed by studies of modern scientists from the University of Warwick (Great Britain). They studied the lives of 6,800 children before they turned 12 and found that those who had nightmares were 3.5 times more likely to suffer from mental illness. And if it happened regularly and intensively – 7 times. However, the reasons for this connection are not yet fully understood.
FIRST SLEEP EXPERIMENTS
In the 18th century, not only mythology and religion, but also science, finally drew attention to sleep. In 1729, French scientist Jean-Jacques d’Ortous de Mairan discovered the 24-hour cycle of leaf closing and opening in a plant. This was the first study of circadian rhythms, which are controlled by an internal biological clock. Later, such rhythms were found in all living beings.
The 19th century gave us the first scientific experiments with sleep. Some of them were pretty violent. So, for example, Maria Manaseina did not let the puppies sleep – they could live in this mode for no more than 6 days. If they were not fed, but allowed to sleep, the puppies lived for 25 days. Similar experiments were carried out on other animals, which caused torment, disruption of various body functions and, ultimately, death.
However, the only organ that remained intact as a result of death from insomnia was the brain, despite the fact that the greatest changes were observed during the transition from wakefulness to sleep in it. Despite the mass of hypotheses, this phenomenon has not yet found an exhaustive explanation.
QUICK AND SLOW SLEEP
In the middle of the twentieth century, the first polysomnographic studies appeared. American physiologists Nathaniel Kleitman and Eugene Aserinsky showed that human sleep is not a single homogeneous state, but a change in two different phases: slow and REM sleep. They differ not only in the different frequency of waves of electrical activity in the brain.
With REM sleep, the eyes of a person under the eyelids move quickly and the skeletal muscles are completely relaxed, and with slow sleep, the eyes are inactive and the muscles are partially relaxed. The first half of the night is the time of slow sleep, for which several centers in the brain are responsible, which, as a result of very complex neurobiological processes, transfer our body from wakefulness to sleep.
The second half of the night is a period of powerful brain activation, REM sleep with dreams that happen to us mainly in the morning. In this case, there is a powerful inhibition of the spinal cord and blockage of sensory systems: a person in REM sleep does not perceive anything from the outside, despite the powerful activation of the brain.
WE DIDN’T ALWAYS SLEEP, AS WE DO NOW
Scientists note that it is natural for a person, as a daytime animal, to sleep, firstly, continuously and, secondly, at night. Sleep cycles are approximately 1.5 hours. Therefore, polyphasic sleep, which has become fashionable among biohackers, when they sleep in snatches of 20 or 30 minutes, can be harmful to health. Although the same daytime sleep (siesta) is interpreted by some scientists as a biological norm inherited from our ancestors.
Culture and civilization have a profound effect on our sleep. According to some studies, preindustrial Europeans slept longer than we do. In addition, they split their night’s sleep into two parts: after midnight they woke up, were awake for a while, and then fell asleep again by dawn.
Sleep phases similar to those of humans are found in mammals and birds, in reptiles and even invertebrates. For example, in octopuses, with which our ancestors parted more than 500 million years ago, scientists have discovered slow and fast sleep, like in humans. During slow sleep, the tentacles and other parts of the body of the cephalopods were relaxed, the pupils were as constricted as possible, and their skin did not change color.
WHAT DREAM IS MORE ANCIENT?
Apparently, first fast and then slow sleep became necessary for living beings at a certain level of development of the nervous system. The predecessor of our slow-wave sleep can be called the state of rest in more primitive organisms: today the sleep of zebrafish, fruit flies, roundworms, etc. is well studied. And the state of activity in cold-blooded, in turn, turned into REM sleep in warm-blooded animals.
The latter is considered more archaic, since its predecessor – activated sleep – predominates in the first weeks of infants’ life. In the 60s, a hypothesis appeared that the brain of the embryo and newborn did not have enough external information to form full-fledged visual and auditory systems of the body.
And the brain compensates for the lack of information during activated sleep. Sleep, as it were, helps the brain to “mature”. However, in general, scientists still do not reliably know why living beings need sleep and why it is so complicated.
One of the most resonant experiments with sleep was staged in 1963 by 17-year-old Randy Gardner, a schoolboy from California, who decided to break the record of a Hawaiian DJ, who managed to stay awake for 260 hours (11 days).
His cognitive abilities have deteriorated and his sensory perception has become distorted. But the guy played basketball perfectly. Perhaps, because he trained day and night. The Hawaiian record was broken by 25 minutes, after which Randy had been sleeping for 14 hours straight.
In 2014, the journalist Tom Michelson from Daily Mail, testing the popular idea of polyphasic sleep, tried to sleep during the day for 4 days – 20 minutes every 4 hours. Already on the second day, attention became scattered, a feeling of constant fatigue and irritability appeared.
The level of cortisol went off scale, the blood pressure increased. The memory worked only 20% compared to the previous values. On the driving simulator, the journalist scored 43 points out of 100, with an initial result of 86.
CAN WE COMMUNICATE IN A DEAM?
36 people from France, Germany, the Netherlands and the United States, divided into 4 independent teams, tried to establish two-way communication during sleep – some of the subjects had the skill of lucid dreaming. The results were recorded using electroencephalogram helmets equipped with electrodes.
As soon as the participants in the experiment entered a lucid dream, they had to give a conditional sign. Scientists asked 158 questions. Correct answers were 18.6%, incorrect – 3.2%, 17.7% were unclear, and 60.8% remained completely unanswered.
In 2013, Japanese scientists managed to read the dreams of 3 volunteers. They were awakened 200 times every 5–6 minutes, measuring the signals of brain activity, capturing images and entering them with the help of a neural network into a single database by categories. During their repeated viewing on the computer screen, the tomograph recorded the activity of the same parts of the brain. Thus, in the future, scientists could already with a probability of 60% determine what exactly a person dreams.
Researchers at the Higher School of Economics at Northumbria and Oxford Universities conducted a study to identify the link between sleep quality, perfectionism, anxiety, and depression. The experiment involved 78 volunteers. Half of the subjects had no sleep problems, and the other half suffered from insomnia for 3 to 10 months.
It turned out that the quality of sleep suffers from perfectionists, as they fall into a vicious circle – the person does not get enough sleep and does not feel well. Negative expectations and fear of not getting enough sleep reinforce the anxiety that keeps you awake again. Even depression, it turns out, is not as detrimental to restful sleep ability as the anxiety inherent in perfectionists.
The American Academy of Sleep Medicine (AASM) recommends sleeping at least 7 hours a day. At Baylor University of Texas, 1,500 people were surveyed and found that sleep duration depended on their religious beliefs. 73% of atheists or agnostics, 65% of believers – 63% of those who consider themselves to be Catholics, and 55% – to Protestant Baptists fulfilled the 7 hours a day norm.