Sleep is a periodically occurring physiological state, characterized by a minimum level of brain activity and a reduced response to stimuli, inherent in humans and other animals. This phenomenon has always attracted people's attention.
The first attempts to scientifically understand the nature of sleep and dreams were undertaken in ancient Greece, but until the second half of the 19th century they were descriptive: scientists only watched the sleeping people, after awakening they asked them about dreams and stated the relevant facts.
The author of the first scientific work on the medical problems of sleep was the Russian researcher M. Manaseina. A book published in 1889 described sleep deprivation experiments: puppies who were deprived of the opportunity to sleep died within 5 days. It has been proven that sleep has a vital function. The researcher refuted the prevailing at that time in science the idea of sleep as a "stop" of brain activity.
The next important stage in the study of sleep was the research of the American physiologist and psychologist N. Kleitman. In his book Sleep and Wakefulness (1936), he formulated the idea of a "basic rest-activity cycle." In the mid 50s. N. Kleitman and his graduate students discovered a special phase of sleep, characterized by rapid eye movements. The scientist considered this phenomenon an intrusion of wakefulness into a single process of sleep, but the French researcher M. Jouvet proved that this phase, which he called paradoxical sleep, is a third state that cannot be reduced either to wakefulness or to "classical" sleep, called slow …
Paradoxical sleep was subjected to experimental study: subjects who were awakened when signs of paradoxical sleep appeared, always remembered their dreams, while after awakening in the phase of slow wave sleep, people claimed that they had not dreamed of anything. So it was established that it is in the phase of paradoxical sleep that a person sees dreams.
Along with sleep deprivation, an important research method in the 20th century. was the study of the brain activity of sleeping people using an electroencephalograph. EEGs taken during sleep showed that slow wave sleep includes four stages. They are characterized not only by different brain rhythms - respiration rate, muscle activity and other physiological parameters also differ.
In other experiments, it has been proven that the perception of signals from the outside world does not stop during sleep. This was determined by the influence of stimuli on dreams. It is noteworthy that such signals have always been transformed in interaction with a person's life experience. For example, in one of these experiments, a hot water bottle was applied to the sleeping person's legs, and he dreamed of a volcanic eruption. It turned out that shortly before participating in the experiment, this subject read a book about volcanoes.
Sleep research continues to this day, sometimes with unexpected results. For example, it was found that when overworked, the duration of slow sleep increases, and if it is necessary to assimilate a large amount of new information, the duration of paradoxical sleep. This made us take a fresh look at the role of both phases. As is always the case in science, each discovery poses new questions for scientists.
