To use a computer analogy, sleeping and particularily REM is your brain's way of running a defrag program. All the information your mind has collected or created is organized.
Also, sleep is your brain's time to balance out it's serotonin levels and replenish its serotonin. Serotonin is very important for mood regulation, several forms of cognition and memory, and digestion.

So essentially, without sleep you'd go nucking futs.
Gandalf_The_Grey Reviewed by Gandalf_The_Grey on . Why do humans actually need to sleep I heard once (not sure if its true) that there was one man who 'never' slept because he believed that humans did not actually need to and we only do because we are used to it from when we are a baby.. What is the actual reason we need sleep is it because our brains need rest.. well say if you didnt sleep for 2 days or 4 days your brain would still work just as good right? Rating: 5