Some time ago, while recording scattered thoughts in an old notebook, I realized how sleeping takes up a big part of the day and that I was not aware of what is going on in the meantime. According to an instruction of the (American) National Sleep Foundation, an average adult needs- although impossible at times- 7-9 hours of daily sleep. Expanding on this thought, sleep occupies about a third of a human’s life. So, I wondered: “What happens when we sleep?”, “Is sleep a comatose state from which we wake up in the morning?”, “How are dreams related to the process of sleep?”
1952: the year when one of the greatest inventions “was born” in the field of sleep science. The new idea was about separating sleep into two phases which were being repeated chronically one after the other. Professor Kleitman from the University of Chicago, with help from the graduate at that time, Aserinski, analysed data from sleeping infants- brain activity, movements of the eyes and muscular activity- to reach a conclusion.
With further research, a hypnogram was made. A hypnogram is a diagram of sleep hours- in the photograph indicatively from 11 p.m. to 7 a.m.- in relation to its individual stages. We observe that each cycle lasts approximately 90 minutes and that the analogy of one type of sleep to the other changes.
Analyzing the diagram, NREM (No Rapid Eye Movement) sleep starts first. It consists of four stages, 3 and 4 being the ones of deep sleep. Cerebral activity becomes ten times lower in relation to the state of consciousness. If we place electrodes in the brain to measure this activity, we observe that the cerebral waves are great in depth resembling sea waves.
During the NREM sleep, the eyes do not move- hence the name- and the stimuli from the sensory organs are obscured to reach the cerebral cortex, their processing centre. This results in the loss of consciousness of the external environment. Responsible for this process is a brain structure called thalamus, through a complex mechanism.
It is an active condition and not a semi-lethargy, as it was believed 50-60 years ago. Every cerebral NREM wave transfers information to various centers of the brain and leads recent experiences from short-term to long-term memory.
After the completion of the NREM sleep, the second stage of sleep follows, the REM sleep (Rapid Eye Movement). The eyes move very fast and the cerebral activity does not differ significantly from being awake. Continuing the previous parallelism, it seems like the sea waves are carrying us away and casting us up. There is complete atony of the striated muscles, but the muscles responsible for the eyes’ movement do not paralyze.
So, what happens while we’re unconscious on the beach? A world of infinite possibilities is laid in front of us. We fly, we cross the world and much more. A film in which we are simultaneously the protagonist and the spectator. The movie’s plot: a combination of the perception of the world, new and old incidents, not only a simple repetition of the day we lived.
Gradually our body says that it is time for a commercial break in our movie. The body returns to the NREM sleep situation and it is time for another dive into the waves. The difference with the previous cycle, though, lies in the fact that the dive is shorter and the film lasts longer. This ping pong repeats itself four times until we wake up.
Until now we’ve talked about the stages of sleep, but what is sleep all in all? Sleep- although we cannot perceive it consciously- is a complex process, essential for survival and well-being. In spite of the progress on research, though, questions like “why do we sleep?” or “why do we dream” are not fully disambiguated yet. In any case, knowledge of the sleep mechanism pitches in the comprehension of the complex way the body functions.
Let’s watch the most peculiar film on the sand, what do you think?
*Information comes from the scientific book “Why we sleep?” by the professor of neuroscience and psychology at the University of California, Berkeley, Matthew Walker
*National Sleep Foundation’s instruction for sleep: https://www.sciencedirect.com/science/article/abs/pii/S2352721815000157
Photography by Simeon Maniatis (@simos_maniatis)