During a first night at a friend's house or at a hotel, on the plane or on the train, it is often difficult to find sleep and sleep peacefully. Of course, this can sometimes be linked to discomfort that interferes with sleep. However, according to one study, it all happens most often in the brain.
We sometimes find ourselves waiting in places like airports, train stations and other waiting rooms. Having time to kill, it is tempting to take a nap, but very often, it turns out to be complicated to achieve. The reason may lie in the discomfort of a stiff chair or cramped space. And yet, many people also struggle to get to sleep and get a good night's sleep even in the optimal comfort of a guest room or hotel. This is called the "first-night effect", and it affects many humans . In 2016, a study published in the journal Current Biology and led by Brown University (United States) looked at what happens in our brains during those first not very peaceful nights.
The cerebral hemispheres don't fall asleep the same way, say researchers than usual when spending a first night in a new place. Usually, the left and right sides find sleep the same way. Thus, it is an asymmetry between the two hemispheres which favors the effect of the first night. The right side does not undergo any alteration, but the left side retains a certain vigilance in the face of an unfamiliar environment. In short, part of the brain remains alert all night and does not allow you to sleep and rest completely.
As part of their study, the scientists recruited eleven volunteers to subject them to advanced neuroimaging techniques . The objective was to study how brain waves react to sound stimuli during sleep. During the tests, the researchers observed that the left side of the brain had different reactions from the right side. For example, the electrical waves from an electroencephalogram travel more in the left side. It is also this same left side that is able to trigger a faster awakening of the body . In other words, in case of danger during a first time in a new environment, the left side plays the role of alarm. It is therefore a real survival mechanism.
In general, after one or two nights in this new environment, the brain relaxes and rests. The latter then simply got used to it and the effects of the first night faded. However, it should be noted that some previous work has observed that this phenomenon can sometimes impact people for a duration of up to four days.
