SLEEP SECRETS

How scientists discovered the secrets of our sleep. This week: The five stages of sleep GERMAN psychiatrist Hans Berger discovered our waking and sleeping brains produce different electrical wave patterns back in 1924.

And Dr Nathaniel Kleitman’s Chicago sleep lab used data about the brain’s electrical activity to show REM (rapid eye movement, usually dreaming) sleep — where the brain is almost as active as when awake in 1953.

But it wasn’t until 1968 that two U.S. scientists, Allan Rechtschaffen and Anthony Kales, revealed sleep stages throughout the night.

There are three non-REM stages of sleep, plus REM sleep. Non-REM stage three sleep is the deepest. If you’re woken during it, you feel disorientated and grouchy. It’s when people sleepwalk or even wet the bed.