As you know, a person has different phases of sleep, among them fast, slow, paradoxical. But observing the fish, scientists found that these representatives of the fauna experience a paradoxical dream.
Each phase of sleep is characterized by activity of the cerebral cortex. In a slow sleep, the brain rests, its activity decreases, and with it the muscles of the body relax, and the heart rate slows down. This is a state of rest in which the body rests.
But a paradoxical dream is almost analogous to wakefulness in the degree of activity of the brain and heart. During this period, eyes and eyelids begin to move quickly, the impression is that a person blinks quickly in a dream. Scientists are inclined to believe that it is in this phase that people dream. Similar periods of sleep are observed in fish, octopuses, flies.
Such phases can be important for living organisms, as they persist in the process of evolution for millions of years. And given how many evolutionary steps separate these animals from humans, it can be said with certainty that such a dream is of great importance.
Stanford University neuroscientist Louis Leng with his colleagues watched the zebrafish fry dream. Thanks to the glow of protein compounds during the life of the brain, scientists were able to trace the work of neurons through a microscope. The choice of fry of these fish was due to the fact that at this stage of their development, they are almost transparent and the movement of organic liquids is easy to see and fix.
The phases were aided by the addition of drugs to the water that were used to induce slow or paradoxical sleep in mammals. True, scientists have found a simpler way out. They simply did not let the fry fall asleep, forced them to stay awake and move, and when the fish were exhausted, they were moved under a microscope. The tired fry immediately fell asleep falling into a state of rest, and scientists could observe the development of the phases of sleep, and fix them in an instrumental way.
It was such observations that made it possible to isolate the different behavior of the brain in fish. At least two conditions were recorded. About this biologists wrote an article in the journal "Nature" ("Nature").
The first phase of sleep in fish resembled a person’s slow sleep. Neurons at this time were only periodically marked by activity. The paradoxical part of sleep was characterized by activity of the whole brain. True, scientists give these phases other names. Nevertheless, the human brain and the fish are different, so many other signs of paradoxical sleep observed in humans are not observed in fish.
