YES, YOU CAN SNOOZE ON YOUR FEET

WE USED to think the brain could be either awake or asleep, nothing in between.

But, in recent years, we have learned that deep sleep and full wakefulness lie at the extremes of a spectrum, and different areas of the brain can be in different states simultaneously.

This seems to be what is at play during parasomnias, such as sleepwalking.

In recent years, it has become apparent that this mixed awake-asleep brain state doesn’t just happen at night.

‘Local’ sleep activity only affecting small areas of the brain can occur in full wakefulness. When rats are kept awake for prolonged periods, nerve cells in the cerebral cortex (the outer layer of the brain involved in thinking and language) fall silent for brief periods, in the same way as they do in deep sleep.

These ‘off-periods’ are associated with increased errors during certain tasks.

Similarly, when sleep-deprived, the awake human brain exhibits changes in activity, meaning that when we are tired, we really are ‘halfasleep’, or perhaps, more accurately, ‘one-tenth asleep’. These changes would certainly explain why we feel less capable when sleep-deprived.