People may feel exhausted and groggy waking up after sleeping in an unfamiliar place like a hotel as if they did not get some sleep at all. According to a study published on April 21 in the journal Current Biology, people feel this way because one hemisphere of the brain stays more awake to keep a close watch on what may happen that will harm the body.

“We know that marine animals and some birds show unihemispheric sleep, one awake and the other asleep,” says Yuka Sasaki of Brown University. “While the human brain doesn’t show the same degree of asymmetry that the brains of marine animals do, the new findings suggest that our brains may have a miniature system of what whales and dolphins have.”

Poor sleep has long been known to occur after sleeping in a new location for the first time. Scientists name this phenomenon the first-night effect and this has not been studied deeper until now.


One may feel groggy after sleeping in a hotel for the fist time because one brain hemisphere stays more awake to keep watch. Credit: Pixabay/estelheitz

The researchers used advanced neuroimaging techniques to study the brain activities during sleep. They observed that the two brain activities have different activities during the first night of sleep.

It turns out that one hemisphere slept more lightly than the other. Apparently, it is always the left side that stays more awake but as of now, the team cannot explain why this is so. Moreover, the one side of the brain that has reduced sleep depth responded better to sounds. Nevertheless, these experiences from the first night of sleep diminishes over time once a person gets used to the place.

However, people can solve this sleep problem by bringing their own pillow or staying in places with similar accommodations as their homes. The researchers also suggest turning one’s night surveillance off to sleep better.

Currently, the research team is employing transcranial magnetic stimulation turn off the awake part of the brain temporarily. They hope to find out if doing this would improve sleep.