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It is hydra a simple creature. Less than half an inch long, its tubular body has one foot at one end and the mouth at the other. The foot sticks to the underwater surface (perhaps a plant or rock) and the mouth, ringed with tentacles, passes through water fleas. He has no brain, no big nervous system.
And yet, shows new research, sleeps. Research by a team from South Korea and Japan has shown that hydra regularly falls into a state of rest that meets the essential criteria for sleep.
In the face of this, that seems impossible. Researchers studying sleep have been looking for the purpose and structure of the brain for more than a century. They have studied the links of sleep memory and learning. They have counted the neural circuits that definitely encourage us to sleep and get us out of there. They have recorded significant changes in brain waves that go through different phases of sleep and have tried to understand what drives them. The mountains of research and people’s daily experiences bear witness to human sleep connection to the brain.
But a view of sleep has emerged as a counterpoint to the brain. Researchers have noticed the molecules created muscles and other tissues can regulate sleep outside the nervous system. Sleep affects the metabolism in the body, which suggests that its effect is not neurological. And a work that has been growing quietly but consistently for decades has shown that simple organisms with fewer and fewer brains spend significant time doing something that looks like sleep. Sometimes their behavior has only been used as a “sleeplike,” but the more details are revealed, the less clear it is why this distinction is necessary.
It seems that simple creatures (now including the brainless hydra) can sleep. And the curious implication of this discovery is that the original function of sleep, which was buried back billions of years in the history of life, could have been very different from the standard conception of man. If sleep does not require a brain, it may be a broader phenomenon than we thought.
Knowing sleep
Sleep does not hibernate, coma or hybridize or any other quiet state, wrote the French sleep scientist Henri Piéron in 1913. Although they all had a similar lack of movement from the skin, each had distinctive features, and that daily interruption. our conscious experience was particularly mysterious. Going without him was foggy, confused, and incapable of clear thinking. For researchers who wanted to know more about sleep, it seemed essential to understand what it did to the brain.
In the middle of the century, if you wanted to study sleep, you became an expert reader of electroencephalograms or EEGs. Placing electrodes on humans, cats, or rats could seemingly accurately tell researchers whether a subject was asleep and what the stage of sleep was. This approach created many perspectives, but it left a bias in science: we learned almost everything about sleep. electrodes could be placed on animals, and the characteristics of sleep were increasingly defined by the brain activity associated with them.
This frustrated Irene Tobler, A sleep physiologist who worked at the University of Zurich in the late 1970s, began studying the behavior of cockroaches, and it is curious whether invertebrates such as insects sleep the way mammals do. Having read Piéron and others, Tobler knew that sleep could also be defined in behavior.
He distilled a set of behavioral criteria to identify sleep without EEG. The sleeping animal does not move. It’s harder to wake up than one to rest. He may take a different attitude than when he is awake or he may look for a specific place to sleep. After waking up he behaves more normally than slow. And Tobler added one of his criteria, drawn from his work with rats: that disturbed animal sleep will then sleep longer or deeper than usual, a phenomenon called sleep homeostasis.
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