Listening U8 Sleep tight

As we get older, we need to sleep _________, although not everyone needs the same amount of sleep.

The two _____ of sleep are REM and NREM.

About 80% of sleep is NREM sleep, when ______ activity slows down.

REM sleep is when _____ happen...

...and is important for _______ our memories.

One of the problems we face today is that there is less ________ than in the past,

and this could _______ our brain.