This is why you feel groggy after sleeping in a new place

http://www.eurekalert.org/pub_releases/2016-04/cp-tiw041416.php

Public Release: 21-Apr-2016
This is why you feel groggy after sleeping in a new place
Cell Press

When people sleep in an unfamiliar place for the first time--a hotel room, for example--they often feel as though they haven't slept as well. Now, researchers reporting in the Cell Press journal Current Biology on April 21 have discovered the reason why: under those conditions, one hemisphere of the brain stays more awake to keep watch.

"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."

Researchers have long recognized that people sleep poorly the first night in a new location, a phenomenon known as the first-night effect. As a result, sleep scientists typically throw out data from the first night a person sleeps in the lab, analyzing data from the second sleep session on.

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during the first night of sleep, the two hemispheres of the brain showed different patterns of activity. One side of the brain slept more lightly than the other. For reasons the researchers don't yet understand, the more awake part of the brain was always the left side.

The degree of asymmetry observed in those brain patterns was related to the difficulty a person experienced in falling asleep, a critical measure in the first-night effect. Importantly, the hemisphere with reduced sleep depth also showed greater response to sounds. Those asymmetries observed during the first night of sleep weren't evident in subsequent sleep sessions.

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