good night’s sleep is more than just eight hours of sweet oblivion at the end of a long, hard day. It’s time for your brain to build up your memory power.
 

That’s important, because when you don’t sleep, your brain struggles to convert the information you’ve collected into long-term memories. A team of international researchers found that just five hours of sleep deprivation can reduce the connections between neurons in the hippocampus, the area of your brain associated with memory formation.

There are two kinds of sleep, and they’re both important for making memories. The first kind happens when your head hits the pillow — you go into non-rapid eye movement (NREM) sleep. That’s when you form “declarative memories” — the who, what, when and where of your life.

After that, you drift into a deeper rapid eye movement (REM) sleep. You’ve never forgotten how to ride a bike or hammer a nail? That’s because of the procedural memories you form during your REM sleep.

Spent the night counting sheep? Don’t worry. Turns out that after three hours of makeup sleep, your memory problems are reversed, and your neuron communication returns to normal.