Why it's so hard to sleep in a new place

People who go to bed wary of potential danger sometimes pledge to sleep “with one eye open.” That might not be too far from the truth. On the first night in a new place, one brain hemisphere stays more awake than the other during deep sleep, in a state of readiness for trouble.

A new study explains “first-night effect,” a phenomenon that poses an inconvenience to business travelers and sleep researchers alike. Sleep is often noticeably worse during the first night in, say, a hotel or a sleep lab. In the lab, researchers usually have to build an “adaptation night” into their studies to do an experiment.

“In Japan they say, ‘if you change your pillow, you can’t sleep’,” says corresponding author Yuka Sasaki, research associate professor of cognitive linguistic and psychological sciences at Brown University. “You don’t sleep very well in a new place. We all know about it.”

Sasaki and lead author Masako Tamaki wanted to figure out why. Over the course of three experiments they used several methods to precisely measure brain activity during two nights of slumber, a week apart, among a total of 35 volunteers. They consistently found that on the first night in the lab, a particular network in the left hemisphere remained more active than in the right hemisphere, specifically during a deep sleep phase known as “slow-wave” sleep.

When the left hemisphere was stimulated with irregular beeping sounds (played in the right ear), that prompted a significantly greater likelihood of waking, and faster action upon waking, than if sounds were played in to the left ear to stimulate the right hemisphere.

In other sleep phases and three other networks tested on the first night, there was no difference in alertness or activity in either hemisphere. On the second night of sleep there was no significant difference between left and right hemispheres even in the “default-mode network” of the left hemisphere, which does make a difference on the first night.

FIRST-NIGHT EFFECT
“To our best knowledge, regional asymmetric slow-wave activity associated with the first-night effect has never been reported in humans,” the authors write in the study that is published in the journal Current Biology.

Researchers used electroencephalography, magnetoencephelography, and magnetic resonance imaging to make unusually high-resolution and sensitive measurements with wide brain coverage.

Though the study evidence appears to document and explain the first-night effect, it doesn’t answer all the questions about it. The researchers only measured the first slow-wave sleep phase, for example. Therefore they don’t know whether the left hemisphere keeps watch all night, or works in shifts with the right later in the night.
Source: www.futurity.org