Dreaming (a possible explanation)

The subject of "why we dream" comes up from time-to-time in my conversations with people.  Although I'm not a neuroscientist and I'm not an expert in this area, I have done some research into this topic and this is what I suspect is happening (a real neuroscientist will probably have better ideas that are based on recent research, so please regard this as a conscious daydream at best).

A friend shared with me his idea that "the brain probably does not know it's dreaming."  My reaction was that I think it differs from one person to the next, but generally I agree that dreams are delusions, which lead to my friend's next question, which was "if they are just a delusion, why do people dream?"

Aided by my attempts to find a reasonable answer to this question, I came up with the following...

The human sleep cycle

Apparently, most humans have a sleep cycle that lasts approximately 2 hours.  It begins in light sleep, then transitions through medium sleep, and finally deep sleep consumes the majority of this cycle.  Another transition through medium sleep occurs before we return to light sleep.  This cycle repeats while we continue to sleep.

As we transition through medium sleep, our brains shrink in preparation for a "natural brain wash" that occurs during the deep sleep phase.  Our second transition through medium sleep is preparation to returning our brains back to their normal size.  In summary, it may also help to think of these medium sleep cycles metaphorically as oceanic tides coming in and going out, respectively.

While in deep sleep, various fluids in our body flow through our brains and wash away toxins and anything else that needs to be flushed out, which probably contributes to why we often feel "well rested" or "refreshed" upon waking up...

Light sleep is when the brain is back to its full size, and when we wake up during this cycle we typically feel more "fresh" and "ready" to begin the day.  If we wake up during the deep or medium sleep cycles, then it's more common to feel "groggy" or even "irritated," and it can take a while to "get up to speed" so-to-speak.  (This could explain why getting an even number of hours of sleep is better for our brains.)

Dreaming

Dreaming, I suspect, is a side-effect of the transition through medium sleep because our synapses and other parts of our brains end up working with different timing (while the brain shrinks or expands) than while we're awake.  This may be the cause of the combinations of fragments of our memories, distortions of some or all of these fragments, and completely new ideas (which may or may not make any sense), which we call "dreams."

As a reminder, this is just an unverified idea, for I don't have expertise in neuroscience, so I could be completely wrong about all of this.  However, I am interested in any perspectives that people with expertise in this field may want to share (please feel free to contact me).