It's uncommon, but there are some people who just have a delayed circadian rhythm and they just - they sleep better during the day then they do at night. So they've - a lot of those people with delayed sleep phase disorder they start to work in bars, they work some of the late night shifts, they sort of adjust to doing it more and more as time goes on.

So, sleep deprivation, and sometimes an insomnia, which is a little bit of a different form, but just getting a lack of sleep, can lead to a number of different decrements.

Well, the actual function of the brain, not so sure yet. There's a lot of different theories about it, but when you talk about psychologically in your brain, a lot of people with insomnia, though not all, report that they can't turn their minds off.

When you're in the more deeper stages of sleep - REM sleep, your body is quiet, but your mind is actually very active. So it's a time when your body and your brain is restoring itself. It's repairing any cell damage that happened during the day, it's really repairing, like I said, repairing your body, but also helps with digestion, helps with memory.

We think is happening in the brain, the way I like to think about it is, it's almost like, you're brain is going through all these stages of sleep and it's developing in children so fast that it's almost like you're shifting gears in a car. And at some point, you actually stall out a little bit, and that's kind of what happens during a night terror.

People went to bed when the sun went down and they woke up when the sun came up. That's what our bodies are naturally programmed to do. However, with all the new stresses in life with electricity, with technology, we tend to override that system and we'll stay up later and we'll get up earlier or later, and we use alarm clocks, we use the light.

Now narcolepsy is really hard though because they're very tired during the day, they're sleepy during the day and it's managed mostly with medications. So we use medications to help them sleep better at night and to stay away during the day. But there are behavioral things you can do also by changing diet, exercise, having an actual nap schedule.