Half of the brain stands guard on the first night in a new place

Sleeping in a different environment is more tiring because the brain is alert to danger signs



The first night sleeping in a different bed is always more tiring. This effect has been known for decades by scientists, since even people without sleep problems have altered results in sleep tests on the first night. Now, researchers showed that this extra fatigue is the result of a protective instinct: in a new place, only half of the brain rests. The other half is alert, ready to react in case of danger.

Researchers at Brown University in the United States carried out tests with 35 students as they slept. The experiments were all made during the phase of deep sleep. It is in this stage of the night that the brain rests, recovers from the day job and begin to fix the most recent memories.

Scientists can distinguish this phase of sleep, because during the period, produce low frequency electromagnetic waves, known as slow wave. But on the first night in the lab, they realized that the left side of the brain produced less slow-wave that right - indicating that he was less immersed in sleep and possibly more alert.

After the first night, the difference between the two sides disappeared. To confirm that one side was more active than the other, the researchers made two more tests. While the students slept, they played short and repeated sounds. At one point, the sound changed tone and became continuous. When we are awake, the brain reacts to this change. On the first night, the brain of the participants also reacted as they slept, but only on the left.

In the last experiment, the researchers played a loud enough to wake someone in light sleep, but did not wake anyone sleeping soundly. If the sound was played in the right ear (connected left side of the brain), volunteers woke up faster.

These tests help to demonstrate for the first time that scientists have imagined: that the brain is alert in a new environment to respond quickly to potential threats. We get tired because one side of the brain stands guard in light, even able to hear noises that would hit on a normal night sleep.

We are not the only ones to have a mental Night Watch: dolphins, seals and various birds can also keep half of the brain awake during the night. One possible explanation is evolutionary: our brain still has the habit of being ready to fight or flee from predators in the jungle - even if you are just starting the holiday in a quiet hotel room.