Good question! However, it is a question that has been ignored for most of the history, until the science of oneirology (the study of dreams) showed up. A statistic shows that people usually forget around 95% or their dreams and their initial accounts of what they have dreamed are always unreliable. But why do we do it? Where do dreams come from? The first breakthrough took place in 1952, when a team of researchers at the University of Chicago discovered an electrical activity which only appeared during a certain stage of the sleep. When the tested subjects were awoken they always said that they were dreaming. The unusual electrical activity was also related to rapid eye movements (REM).
An interesting fact was the brain’s activity during the REM sleep, which was almost identical to the times when it was awake. There was only one noticeable difference: the brain stopped producing important chemicals as serotonin and histamine, causing you to experience a sleep paralysis. Your imagination runs wild, but you cannot move. This aspect is extremely important, because it opens the door to some highly unusual behaviors that caused plenty of ludicrous theories over the time, including possessions, outer-body experiences, Angels and so on. The phenomenon is call REM atopia.
- Sleep walking
One such interesting behavior is when your brain fails at blocking chemical productions during sleep, which will cause your muscles to be fully active. That is when sleepwalking shows up.
- Awake and paralyzed
The same thing can make you wake up and be aware of what is happening around you, but you are completely paralyzed.
- Lucid dreams
And then there is the lucid dream, where you are actually aware of the fact that you are dreaming and you can change anything you want inside your dream. In fact, lucid dreaming seems so appealing that there are even guides showing you how to achieve it, since it is not quite an easy task it seems.
Also, while sleep deprivation can have serious consequences even leading to death, REM deprivation can cause you to experience memory loss. The most accepted theory today is that during night the subconscious rearranges the information gathered during the day, sorts the important things and throws away the irrelevant stuff. So be careful to sleep well and don’t forget to dream.