'The origin of sleep' could be traced back to 450 million years ago
'Sleep' is quite commonplace for humans, but it is strange that most mammals lose their consciousness for several hours a day. According to a study published in Nature on July 10, 2019, fish slept like humans, and human sleep may have been inherited from fish, a distant ancestor, over 450 million years It is suggested that there is.
Neural signatures of sleep in zebrafish | Nature
Slumbering zebrafish may offer clues to the origins of sleep
Human beings is a non-REM sleep and light sleep is a deep sleep REM sleep and repeat. Previous studies have suggested that rem sleep is limited to humans and other mammals and birds. It was thought that REM sleep was acquired in the process of evolution that the brain is awake while the body is asleep.
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The current research is from the research team at the Sleep Science and Medical Center at Stanford University in the United States, and Professor Koichi Kawakami from the National Institute of Genetics in Japan is a coauthor. The research team observed the sleep using a zebrafish fry that is clear and suitable for observation in the body.
by Oregon State University
The activity of neurons in the brain increases the calcium concentration, so the experiment used zebrafish genetically engineered to glow green in response to calcium. The research team confined the zebrafish in a gel like gelatin so as not to move around, and measured data on brain activity, heart rate, muscle activity, and eye movement. In addition, to ensure that the zebrafish is asleep, the research team kept waking zebrafish from falling asleep, creating a 'sleepy' condition.
As a result of the measurement, it was confirmed that this sleepy zebrafish performs REM sleep and non-REM sleep, and the heart rate is halved during non-REM sleep, and it has also been found that the muscles of the body relax. This is the opposite of the theory that only birds and mammals have acquired REM sleep in evolution.
It has been thought that REM sleep has been acquired in the process of evolution until now, but from the results of this experiment, the research team suggested that the origin of sleep could be traced back to about 450 million years before the birth of fish. doing. 'The ability to visually investigate how neurons in drug-treated animals are activated is a great advance,' said Paul Franken, neurologist at the University of Lausanne, Switzerland.