Have you ever heard of “sleeping with one eye open” in a dangerous situation? It turns out your brain thinks anything new is a dangerous situation, and that’s why it’s hard to sleep well on the first night in a strange place.
A study from Brown University looked at the phenomena, which sleep experts call the “first night effect”. Because of this effect, sleep is often noticeably worse during the first night in, say, a hotel or a sleep lab. It’s because of this effect that researchers usually have to build an “adaptation night” into their studies to do their experiments. This time around, the team at Brown investigated the first-night effect, rather than factoring it out.
“In Japan they say, ‘if you change your pillow, you can’t sleep,’” said corresponding author Yuka Sasaki, research associate professor of cognitive linguistic and psychological sciences at Brown. “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 their team 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 researchers stimulated the left hemisphere 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. The testing, in other words, pinpointed a first-night-only effect specifically in the default-mode network of the left hemisphere during the slow-wave phase.
The volunteers did not report any unusual discomfort or anxiety in surveys. They were all screened for general mental health before enrollment in the research to ensure their typical sleep was likely to be normal.
Though the study evidence appears to document and explain the first-night effect, it doesn’t answer all the questions about it, Sasaki acknowledged. 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.
“It is possible that that the surveillance hemisphere may alternate,” Sasaki said.
Sasaki said it’s not known yet why the brain only maintains an alert state in just one hemisphere – whether it’s always the left or in alternation with the right. There are many examples among animals, however, of hemispheric asymmetry during slow-wave sleep. Marine mammals exhibit it, Sasaki said, presumably because they regularly need to resurface to breathe, even during sleep.
Now it’s been found in humans as a first-night phenomenon.
“The present study has demonstrated that when we are in a novel environment, inter-hemispheric asymmetry occurs in regional slow-wave activity, vigilance and responsiveness, as a night watch to protect ourselves,” the study concludes.
So, what can you do to alleviate the first night effect, so you can enjoy your vacation more? One possibility that could (but isn’t guaranteed to) work is to bring your pillow with you on vacation. Then, at least your head will be laying on something familiar!