Only one of the hemispheres sleeps deeply in a person’s place.

Biologists from Brown University found that the brain of a person sleeping in an unfamiliar place does not function as usual. The left hemisphere does not completely switch to sleep and, according to one of the researchers, is “slightly stronger” awake than the right one.

Back in the 1970s, biologists studying marine mammals found that dolphins in a state of slow sleep alternately have only one of the two hemispheres of the brain. It is believed that the reason for this is that dolphins, like other marine mammals, are forced from time to time to rise to the surface of the water for breathing.

People do not need to float to breathe, but everyone felt on himself or heard from his friends about the unpleasant sensations that arise after spending the night in a new place. Often people complain that they are tired and have not slept. Physiologists have known the “first night effect” since when they began to study the sleep of people in laboratories. The results of the first night of sleep are simply excluded from consideration, because at this time sleep is often disturbed.

Yuka Sasaki [Yuka Sasaki], the author of this work, decided to study in detail what is happening exactly during the first night of sleep at a new place, for which 35 university students, the favorite experimental subjects of all scientists, scanned the brain waves with their colleagues.

Scientists interested in brain activity during slow sleep. Slow sleep is the first thing a person feels after falling asleep. It consists of four stages. It is believed that slow sleep is associated with the restoration of energy consumption. Studies have shown that it is the phase of slow sleep that is key to anchoring conscious “declarative” memories. Behind a slow sleep there is a fast sleep, or a stage of fast eye movements.

Sasaki and colleagues found that during the first night in the laboratory, in certain parts of the right hemisphere of the brain, the activity of slow waves (theta rhythms) was higher than in the corresponding areas of the left hemisphere of the brain. In the following nights, this difference completely disappeared.

To confirm the findings of the students put two experiments related to sound. At first, the monotonous sound was lost to the sleeping one, which suddenly changed into a different tone. It is known that the shallow brain responds to such stimulation. The students also observed the reaction of the brain - but only its left half.

Then, the sleeping sound was played louder, able to awaken a shallow sleeping person. As a result, only those who got lost in the right ear connected with the left hemisphere of the brain would wake up.

Commenting on the work of scientists, Niels Rattenborg, who studies birds sleeping at the Max Planck Ornithological Institute, said that earlier no one had been able to demonstrate the difference in brain hemispheres during sleep in humans, in particular, the possibility of only one hemisphere to rest.

Rattenborg noted that such properties were previously attributed only to dolphins, some other marine mammals (seals), as well as some birds. He himself several years ago was engaged in the study of sleep in ducks , and found that the ducks placed in a row sleep differently. Those birds that had their companions on either side slept soundly. The extreme slept only one half of the brain, and the waking eye followed the approach of predators.

And although people no longer need to worry about predators, the evolutionary fixed instinct “the night is dark and full of horrors” does not allow us to rest easy in an unfamiliar environment.