Have you ever wondered why sleeping in an unfamiliar place is generally uncomfortable and leaves you exhausted the next morning? Turns out, half of our brain stays awake to keep watch in such a situation, interrupting our normal sleeping patterns.
For the research, published in the journal Current Biology, a series of lab tests were performed and the brain activity watched by researchers using ultra-sensitive neuroimaging.
They discovered that half of each participant’s brain — specifically, the left hemisphere — remained active during sleep on the first night in the lab.
The effects seem to stay on only for the first night. The second night of sleep showed no significant difference between left and right hemispheres.
The researchers played sounds into each ear of the sleeping participants to test for alertness.
They found that when sounds were administered into the right ear — that is, stimulating the left side of the brain — the participants were more likely to wake from sleep.
This hemispheric switching — known as inter-hemispheric asymmetry — is common in the animal world, particularly in marine mammals, who need to breathe regularly even during sleep, the researchers explained.
“The 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,” said one of the researchers Yuka Sasaki, associate professor at Brown University in the US.
The team only studied early sleep phases, so they’re still unsure as to whether the left side of the brain stays alert throughout the entire first night, or switches to give the right side a chance.
“It is possible that the surveillance hemisphere may alternate,” Sasaki noted.
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