Half of the brain awake even during sleep
Ever experienced tossing and turning in bed while staying in a new place and getting up the next morning feeling the after effects of inadequate overnight sleep? Well, a new study has found the cause: New surroundings can interrupt our normal sleeping patterns as half of our brain stays awake to keep watch!
For example, after sleeping in a hotel room, people often feel as though they haven’t slept well and remain groggy throughout the next morning. This is known as the ‘first-night effect’.
For the results, 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 go.
“It is possible that the surveillance hemisphere may alternate,” Sasaki noted.