Re: What does our brain do while we're asleep?

	Pretty much the same thing it does while you're awake.  It sends 
signals down your spinal cord to control your heartbeat, your breathing, 
all the important stuff that keeps you alive and functioning properly.
	Sleep is composed of 2 easily distinguished stages or phases. One is 
characterized by slow EEG activity (a measure of brain activity), general 
muscle relaxation but with sporadic movements of the body, and deep breathing, 
and is usually referred to as slow wave sleep; while the other stage shows very 
fast EEG activity, similar to how our brain patterns look when we're awake, 
and skeletal muscle paralysis--those are the ones in your arms and legs 
which you can consciously control (but not your heart, and not the smooth 
muscles in your stomach or intestines, and also not the eyes, which move around 
rapidly--none of those are paralyzed).  It does this so you won't move around 
and hurt yourself in your sleep by falling out of the bed or something.  
Sometimes this paralysis fails in people who sleepwalk (noone is exactly sure 
how or why).  This stage is known as rapid eye movement sleep REM sleep) or as 
you may have heard, the main type of sleep where you do the most vivid dreaming.
     Let's talk more about the changes in brainwaves, the patterns of 
electricity that carries the signals between different parts of your brain. 
While you're awake, if you recorded your brainwaves and played them back 
through your stereo, they would sound like static. (If you listened to only one 
brain cell at a time, the signals might make sense, but that's another story.)  
The same thing would happen if you tried to listen to all the traffic on the 
Internet at once.  All of those different signals mixed together is called 
desynchronized activity.  While you're in slow wave sleep, all of that furious 
activity collapses down to three or four powerful rhythms.  It becomes 
synchronized, meaning most of the cells start to fire electrical signals 
together--on, off, on, off, on, off, on, off... instead of off, off, on, on, 
on, on, off, off...  

However when you enter REM sleep your brain waves start to look like you're 
awake again!  Dreaming may be a way of making your memories permanent, like 
writing them from computer memory onto the hard drive, but nobody knows for 
sure.
	Try running a search on Google.  Here's a couple of sites I found 
there: A brief 
Introduction to Sleep 
 If you look at their graph of sleep, you can
see REM sleep represented by the blue bars, and slow wave sleep by the red 
lines.  As you will see, there are different levels within slow wave sleep, 4 
being the deepest sleep and 1 being the lightest sleep (at 0 you are awake).  
http://www.stanford.edu/~dement/ 
http://www.sleepnet.com/            
(This one looks especially good, because you can ask them questions, too)