We all know people who look like they can nod off with their eyes open. These exceptions aside, we generally think of sleep as a switch with two settings – you’re either asleep or awake. But Vladyslav Vyazovskiy from the University of Wisconsin-Madison has found that sleep is more complicated than that.
By studying the brains of sleep-deprived rats, Vyazovskiy found that individual neurons can effectively fall asleep, going “offline” while those around them carrying on firing. Even if the rats are awake, parts of their brain can be taking a nap. What we know as “sleep” is the global version of something that happens throughout the brain at a local level.
Our neurons exist in two states. When they’re “on”, they have an electric charge across their membranes and they fire erratically and often. When they’re “off”, the charge disappears and they stop firing altogether. When we’re awake, our neurons are mostly on. When we’re asleep, they cycle between the two states, in time with one another. Scientists can detect these flips as “slow waves” on an electroencephalogram (EEG).
To find out what happens in a sleep-deprived brain, Vyazovskiy kept rats …
