No one can stay awake forever. While we’re awake, our need for sleep gradually increases. If we deprive ourselves of sleep, our brain functions – such as attention or judgement – are impaired, and sleep becomes irresistible. No matter whether we are on a couch or at work – if we ignore our need for sleep, we ultimately crash.

Although sleep is vital, until now it hasn’t been known which structure of the brain tells us when we are tired. But our recent study has shown in laboratory mice that the cerebral cortex, which is responsible for the most complex brain functions – including perception, language, thought and episodic memory – helps us track our need for sleep.