Most people, when traveling, complain about not sleeping well. Regardless if we chose a comfortable hotel room or the quiet home of a relative, sleeping on a new mattress is difficult, at least until we get used to it. In fact, even if we manage to sleep, the next day we wake up with a heavy feeling of sleepiness and fatigue, due to the fact that we have not rested completely.
Now, researchers at the Georgia Institute of Technology have discovered the cause of this problem. It seems that when we sleep in a new bed, away from home, one of our cerebral hemispheres remains vigilant, it doesn’t unplug completely, remains vigilant to protect us from potential dangers we might encounter in an environment that is unfamiliar.
The first-night effect
The researchers recruited 35 young men and monitored their brain activity while they slept in the laboratory using advanced neuroimaging techniques. These neuroscientists made sure that people hear a beep in the right ear, which normally awakened them. But people didn’t notice the same signal when it was sent to the left ear. This indicates that a hemisphere remains awake while the other is disconnected.
These results suggest that during deep sleep the left hemisphere was not completely disconnected. In fact, it is not the first time that these types of brain asymmetries are documented. It is known that some animals, such as dolphins, are able to rest disconnecting alternately each hemisphere of the brain. So, while one hemisphere is disconnected the other takes over and is responsible for supervising.
This experiment revealed another interesting fact: this phenomenon was observed only during the first night. Once a person gets used to the new bed and the environment, is able to sleep deeply and both hemispheres are disconnected. It is what is known as “first-night effect”.
Why the left hemisphere is disconnected?
Researchers believe it depends on an evolutionary strategy, in fact, centuries ago deep sleep could be a serious danger. Therefore, it would be a legacy of our ancestors, a kind of nightly sixth sense which becomes active when we sleep in a new bed, in an environment that is unfamiliar.
Moreover, in the experiment it was found that this “night guardian” is really effective because in case of rare auditory signals the left hemisphere launched the alarm to wake up the person and make sure he’s safe.
At this point you might wonder why the left hemisphere is responsible for monitoring our sleep?
Neuroscientists believe that the explanation lies in the default neural network, which involves some brain regions to make sure that this will continue to work when we are not fully aware, as when we sleep, we are anesthetized or let our mind wander freely.
This network is responsible to prepare ourselves react to dangerous situations. In practice, it activates itself to protect us when we disconnect from reality or consciously lower the guard.
We know also that connections of the left hemisphere with the default neural network are stronger than those established by the right hemisphere, which is why this part of the brain remains on alert, because it would be more effective to wake us up in case of danger.
How to avoid the effect of the first night?
The researchers suggest that this effect cannot be avoided completely, but there are some tricks for trying to fool the brain and turn it complacent. For example, you can bring with you your own pillow and sleep with that, or use a fragrance that remembers the smell of your home. These details will transmit you a feeling of familiarity, so your brain will feel more comfortable and secure.
If you travel often, a solution is to choose similar rooms whenever possible. This reduces the feeling of novelty that alarms the brain and prevents sleep.
Sources:
Tamaki, M. et. Al. (2016) Night Watch in One Brain Hemisphere during Sleep Associated with the First-Night Effect in Humans. Current Biology.
Liu, H. et. Al. (2009) Evidence from intrinsic activity that asymmetry of the human brain is controlled by multiple factors. Proc. Natl. Acad. Sci.; 106: 20499–20503.
