Sleep seems simple enough: at night, you close your eyes and you fall asleep. However, those with insomnia or jet lag have a more complicated time with it.

It turns out that sleep is much more complex than we initially thought. And now, we know that in addition to a master clock that tells our body when and how to sleep, we also have a local clock that affects sleep, too.

All animals have an internal circadian clock that governs what happens when inside the body. That master clock reacts to the presence of light, or lack thereof, and tells us when it's time to sleep and when it's time to wake up. This master clock resides in the suprachiasmatic nucleus (SCN) portion of the brain and affects the clocks of our entire body, from sleep cycles to metabolism.

But now, scientists have evidence of a secondary clock, a "local clock," that also plays a part in when we sleep.

Outside the SCN part of the brain, there's a part called the tuberomamillary nucleus (TMN) that contains neurons that do nothing when the body is asleep. However, during waking hours, these neurons release histamine, which keeps us awake. And we now know this, thanks to an experiment with mice.

Researchers got rid of the Bmal1 gene in the these specific neurons in mice. This gene helps regulate sleep. Those mice had higher levels of histamine in their bodies, resulting in them being awake longer than normal. Their sleep was also restless and they didn't recover well from sleeplessness. Basically, by removing that gene, the scientists created insomnia-ridden mice.

These researchers also provided more evidence that lack of sleep affects memory. Those mice without the Bmal1 gene performed poorly in object recognition tests. Mice only respond to new objects in their environment and generally ignore older objects. However, those mice without Bmal1 responded to all objects, old and new, suggesting that they forgot those objects that were old to them.

This research suggests that this local clock is as important in getting a good night's sleep as the master clock.

"Ultimately, understanding local clocks better might enable us to target them to help people have a better night's sleep," says Professor Bill Wisden from Imperial College London.

Getting a good night's sleep means better health, both physically and mentally. Better sleep not only improves memory and creativity, but also helps in maintaining a healthy weight, lower stress and prevent depression.

[Photo Credit: Robin Burks/Flickr]