Scientific American presents Everyday Einstein by Quick & Dirty Tips. Scientific American and Quick & Dirty Tips are both Macmillan companies.

Hi, I'm Dr. Sabrina Stierwalt, and I'm Everyday Einstein bringing you Quick and Dirty Tips to help you make sense of science.

As an astrophysicist, I often work all night when the telescope calls. Unfortunately for me, the rest of the world doesn't follow my lead. If I need to grab groceries, I'm still going to have to do that during daytime hours. And my toddler has never looked at me at 6am and said, "It's OK, mommy, you just rest today. I'll feed myself."

So for those of us who occassionally spend late nights working on a project or binge-watching our favorite television show, can naps help us recover those lost resting hours?

What Sleep Does for the Brain
Sleep is known to give us energy, increase our alertness, and improve our mood, as well as our memory and reaction time. Getting a full night's rest can also help you get fit and make better nutritional choices.

So how does sleep do all of that?

Our sleep is not the same throughout the night, instead it goes through cycles of REM and non-REM sleep. REM stands for "Rapid Eye Movement" and refers to the motions of our eyes which dart back and forth during this sleep phase.

Most or about 75% of the night is spent in non-REM sleep (called NREM). Our breathing slows, our blood pressure drops, and our muscles relax. Our body goes into repair mode bringing blood to our muscles, rebuilding tissue, and releasing hormones like those that help with growth and development. Hormones regulating our appetite are also released which may contribute to the link between lack of sleep and weight gain (in addition to, of course, late night snacking).

After the first 90 minutes of sleep, we reach the REM phase which is unique to mammals like ourselves. Our brain acts awake - this is the stage when dreams can occur - but our bodies are immobilized. Although called "rapid," our eye movements are not actually any faster than they are during our wakeful periods. Researchers have found that blind people, even though their ocular activity is very different throughout the day, still undergo the same eye movements during REM sleep.

Studies have shown that while NREM sleep may be the most restorative, REM sleep appears to be more closely linked to improvements in creativity and problem solving skills.

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