When you sleep away from home, you usually feel less comfortable and can wake up groggy. Now, scientists have discovered that when you sleep away from home, one brain hemisphere remains more awake than the other during deep sleep.
In this latest study, the researchers set out to find out why you don't sleep very well in a new place. Over the course of three experiments, the scientists used several methods to measure brain activity during two nights of sleep. Both of these nights were a week apart, and a total of 35 volunteers were studied.
So, what did they find? It turns out that on the first night in the lab, a particular network in the left hemisphere of the brain remained more active than in the right hemisphere. More specifically, this was particularly noticeable during a sleep phase known as "slow-wave" sleep.
That's not all, either. The researchers found that during this more awake state, people were more likely to wake up after hearing an odd noise and were faster at acting upon waking. This, in particular, highlights the fact that this response may be a way to help aid our ancestors with survival.
"In Japan they say, 'if you change your pillow you can't sleep,'" said Yuka Sasaki of Brown University, one of the researchers involved in the new study. "You don't sleep very well in a new place. We all know about it."
Surprisingly, though, the researchers found that there was no difference in alertness or activity in other sleep phases. In addition, on the second night of sleep in a different place there was no significant different between left and right hemispheres even in the "default-mode network" of the left hemisphere.
While the findings do document this effect, they don't answer all the questions about it. For example, why does the brain only maintain an alert state in just one hemisphere? With that said, further studies may tell researchers a bit more about why this is. At this point, though, researchers are excited to find that the first-night phenomenon is present in humans.
The findings were published in the April 21 issue of the journal Current Biology.
