When you sleep in unfamiliar surroundings, only half your brain gets a good night’s rest. “The left side seems to be more awake than the right side,” says Yuka Sasaki, associate professor of cognitive, linguistic and psychological sciences, Brown University.
The finding helps explain why people tend to feel tired after sleeping in a new place. And it suggests people have something in common with birds and sea mammals, which frequently put half their brain to sleep, referred to as unihemispheric sleep.
One stage of deep slumber is known as slow-wave sleep. In this stage, a group of nerve cells in the left side of the brain showed less sleep-related activity than the same group on the right side. That suggests the left side of the brain was a lighter sleeper. This imbalance disappeared by the second right.
Both the right and the left sides of the brain have a “default mode network”, a collection of nerve cells that are active when the brain isn’t focused on doing anything special. Researchers found that the default mode network in the left side of the brain reacted faster to quiet sounds on the first night of sleep. And a sleeper’s response times were faster on the first night than on the second.
This alertness makes sense, says Jerome Siegel, who studies sleep at the University of California. “Sleep is only adaptive if it doesn’t produce risks that outweigh its benefits,” he says. And safe sleep often means keeping an eye on the environment.
Picture Credit : Google
