Those young people who stay up late are worse than octopuses

When an octopus sleeps, its skin becomes colorful. | SYLVIA MEDEIROS

Author｜Chen Shurui, Nagoya University, Japan

We have all heard the story of Zhuangzi dreaming of a butterfly. Zhuangzi was confused after waking up, wondering whether he dreamed of becoming a butterfly or the butterfly dreamed of becoming him. We don’t know if butterflies can dream, but perhaps octopuses can.

A study published in the journal iScience found that octopuses not only sleep, but they may also dream, and their bodies become bright and colorful during their sleep. What's even more amazing is that the sleep cycle of octopuses has many similarities to that of humans.

Sleeping is not as simple as lying down on the bed.

For humans, sleep is more than just a respite from busy work. We all know that if we have a good night's sleep the night before, we will wake up refreshed and full of energy in the morning. On the contrary, insomnia or lack of sleep will make people physically and mentally exhausted and depressed. What is the magical effect of sleep that allows the body and brain to repair?

If sleep has cycles and rules, why do we sometimes feel sleepy or feel very sleepy after waking up even if we keep a fixed sleep time every day? To answer these questions, we must first understand the human sleep cycle.

When the busy streets are no longer noisy and tired people feel drowsy, the body will start to sleep. The start-up process usually takes 30 minutes. If you hear a noise or your body is touched, you will be easily disturbed and return to the awake state. If everything is fine, you will successfully enter the sleep state.

At the beginning of the sleep state, the brain begins to become inactive, muscle activity gradually weakens, and the eyeballs no longer move. Medically, this period is called non-rapid eye movement sleep (NREM), also known as slow-wave sleep. This stage lasts about 80 to 120 minutes, after which the body can enter a deeper level of rest. Interestingly, after entering a deeper sleep, the brain becomes active, the eyeballs keep moving at a frequency of about 7 times per minute, the heart rate, heart pumping, arterial blood pressure and respiratory rate become irregular, and enter the so-called rapid eye movement sleep (REM) stage. In a sleep cycle, the two sleep modes alternate, and the proportion of the REM stage gradually increases as sleep continues. We will go through about 3 to 5 sleep cycles a night, each round is about 2 hours.

The human body's sleep is divided into stages, from wakefulness to rapid eye movement sleep (REM). ｜vitruvi.com

Although the brain works faster during the REM stage, it is actually more conducive to restoring energy. This is because the brain will carry out high-intensity neural information processing activities at this time, which helps to organize and consolidate memories, making it easier for people to concentrate after waking up and have better judgment and analysis capabilities. And this process is often achieved through dreaming, which is what we often say "thinking during the day, dreaming at night." If awakened during the REM stage, people can often narrate dreams full of storylines and show better attention and creativity after waking up. However, if the sleep regulation mechanism is disordered and the proportion of REM in the sleep cycle is too small, memory consolidation disorders will occur, and it will be difficult to complete complex tasks after waking up, and they will still be exhausted. Therefore, it can be said that a regular sleep cycle is a key factor in ensuring sleep quality.

In the REM stage, the brain performs high-intensity neural information processing activities through dreaming, which helps to organize and consolidate memories. ｜zenbev.com

The little octopus has a colorful dream

In fact, it is not only humans who need to sleep. Scientists have found that there is no animal in nature that does not need to sleep. Therefore, they have been trying to study the sleep cycles of various animals to uncover the mystery of sleep. Cephalopods such as octopuses are particularly interesting. They are far below mammals in the evolutionary level. If even octopuses have a sleep cycle similar to that of humans, wouldn’t it be easier to understand the significance of sleep cycles to brain evolution and why all animals need sleep?

Because it is difficult to obtain electrophysiological data from these animals, related research has been hampered. Until recently, Brazilian scientists brought wild deep-sea octopuses back to the laboratory and created a quiet environment conducive to sleep for them. Only then were they able to observe the sleep status of octopuses through eye movements, skin color changes, and the numerical difference in the minimum stimulus required to wake the octopus.

The researchers found that sleeping octopuses also have periodic changes, and this process is similar to humans in many details. Octopus sleep can be divided into two stages: a quiet period and an active period, which correspond to the NREM and REM periods of human sleep respectively. The quiet period lasts about 7 minutes on average, during which the octopus's skin is pale and its pupils are closed. The active period that follows is much shorter, only about 40 seconds, during which the skin color and texture are full of changes, the eyeballs are constantly moving, and the muscles will twitch. In other words, if octopuses really dream, their bodies will appear in beautiful colors when they dream.

In this way, the little octopus actually has a colorful dream - although it may be just a short video or animated picture of dozens of seconds. Don't be a night owl, embrace colorful dreams. Although the mystery of sleep has not been fully revealed, the fact that octopuses also enjoy sleep so much shows that sleep is indeed very important for animals.

Each of us spends about 1/3 of our lives sleeping. It is so common that many people underestimate their sleep problems. Occasional irregular sleep may not cause physical discomfort, but as we age, or if staying up late gradually becomes a habit, physical and mental recovery will become slower. This will not only affect work efficiency and cause depression, but also threaten physical health and even cause sudden death. The next time you want to work overtime at the cost of your health, perhaps you should remind yourself to learn from the little octopus, ensure sleep, and have a good dream. Life may become more colorful because of this.

Source: Lorenza Walke

r Editor｜Chen Tianzhen

References

[1]Cyclic alternation of quiet and active sleep states in the octopushttps://www.cell.com/iscience/fulltext/S2589-0042(21)00191-7?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS2589004221001917%3Fshowall%3Dtrue

[2]Octopus sleep includes a frenzied, colorful, 'active' stagehttps://www.sciencenews.org/article/octopus-sleep-stages-active-color-quiet-rem-brain

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