Ever wonder why we sleep?  I do.  Sometimes it amuses me to ponder how much more I’d get done if I didn’t have to sleep, especially on a day when I have woken up at oh-dark-thirty to head to the airport.

At any rate, here’s an interesting read on the topic.  Excerpt:

…despite all that has been written on the subject and all the effort devoted to studying the phenomenon scientifically, we do not have a clear answer to a question that would seem to be central to understanding the human experience: “Why do we sleep?”

To answer that we need to first ask what sleep is, and what its essential characteristics are. We know that it is probably evolutionarily conserved, meaning that it has persisted throughout evolutionary history ever since it first evolved. Many scientists also think it is universal among animals, though it has been studied systematically only in a small number of species. Sleep may show up under different guises in different species. Dolphins, for instance, may be able to sleep “unihemispherically” — falling asleep with one half of their brains while the other half remains awake. This allows them to perform complex activities, such as swimming to the surface of the ocean to breathe, without waking up. The nematode worm C. elegans enters into a sleep-like lethargus before molting. In many species, including humans, sleep is generally associated with certain postures, such as lying down, and immobility.

It’s not as easy as you might think to tell if an animal is sleeping. A crude but effective way is to test if an animal is “disconnected” from its environment by providing some stimulation that would typically provoke a strong reaction, such as an unexpected noise. If the animal does not react, there is a good chance that it is genuinely disconnected — and thus sleeping, rather than merely resting. Scientists consider such a reversible disconnection from the environment to be a defining feature of sleep. (An irreversible disconnection from the environment would be a coma.)

Why would animals periodically disconnect from the environment?

Maybe disconnecting from the environment is reason enough.

I studied biology years ago, and maintain an interest in the topic.  While behavior was my focus when I was still in the field, I never studied the phenomenon of sleep, other than engaging in it myself.  But here’s the main theory described in this article:

Still, learning, memory, and cognitive ability seem to be promising areas for trying to find an essential function of sleep. One recent proposal that attempts to draw these areas together into a single whole is the Synaptic Homeostasis Hypothesis (SHY), originally put forward by Giulio Tononi and Chiara Cirelli in 2003. (Full disclosure: I did my doctoral research in Tononi and Cirelli’s Center for Sleep and Consciousness at the University of Wisconsin–Madison, though SHY was not my focus.)

To my mind, SHY stands apart from other scientific hypotheses about sleep because of its scope and its explanatory elegance. And, despite the fact that elegance is an important feature of scientific theories, there are surprisingly few elegant theories in neuroscience. This may be because so many neuroscientists treat the brain as a modular kludge, focusing on one specific part of the brain as pertaining to their research specifically. SHY, by contrast, is about neural networks in general.

In other words, sleep fulfills the vital function of sort of “resetting” the nervous system, allowing the collation of information gathered during the waking period.  That’s important in the learning and analysis process.  I’ve experienced it myself; the concept of “sleeping on it” is as old as the ages.

Interesting stuff.  A good night’s sleep my do us a lot more good than we think.