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I recently did a bunch of research on the difference between dreaming and waking states, so I will share the essence of what I learned and attempt to answer Adityas question about why we can behave logically in the illogical world of dreams.

As we learned in class REM sleep is the deepest stage of sleep, characterized by the highest sensory thresholds and lowest motor output. It is also the phase of sleep when dreaming occurs. The brainstem is responsible for stopping the motor signals sent by the brain from being reaching the body. It also (according to the current research) generates random sensory signals. These signals do not seem "weird" to the brain because all sensory signals get relayed through the brain stem when we are awake. The brain is dupped into believing that these internally generated signals being produced by the brainstem are real signals being relayed from the outside world. This is why dreams feel, look, sound, and smell so real. These internally generated sensory signals pass from the brainstem into the forebrain. The forebrain needs to make sense of this input, so it weaves it into a story. This explains the narrative nature of dreams. The brainstem generates a picture of a monster, sends it to the forebrain, the forebrain says "ah monster, run away!", it sends motor signals to your legs to run, and the brainstem intercepts and stops the motor signals.

The logical behavior in our dreams can be attributed to the story building role of the forebrain. The forebrain is no dummy, if it is sent a picture of a bike and a monster it will have us jumping on the bike and riding like theres no tomorrow. This is because in dreams we have access to pretty much all of the faculties that we do when we are awake. We still know what our school looks like, or that biking is faster than walking.

One crucial area of the brain that is inactivated during dreaming an area of the frontal lobe responsible for autobiographical knowledge and judgement. This explains why we do not question the bizarreness of our dreams. We lack the capacity to pass judgement on our surroundings ("could a dog really have three heads?"), and we lack self knowledge ("my dog doesnt have three heads, so this cant be real").

This theory is supported by research on lucid dreams, a lucid dream is a type of dream where the dreamer is aware that they are dreaming. Lucid dreamers report that they often obtain lucidity by realizing that something in their surroundings is too bizarre to be real. They are able to pass judgement and realize they are in a dream state. The onset of lucid dreaming is characterized by high levels of cortical arousal and activity in the area of the frontal lobe that is usually inactive.

I like this model of dreaming/lucid dreaming/waking states, and their relationships. I also am tempted to believe that sleep is a time when the brain reorganizes, sorts, and stores memories, and that dreaming is a product of this memory sorting. It would explain why my dreams always contain images from the previous day. I'm not sure how that theory could be reconsiled with the previously explained theory. One idea may be that when the memories are getting sorted some pop into awareness, and we literally relive those memories as they flash before our minds eye, and maybe the brain stem creates the relevant sensory input to match that memory? Just an idea.

I know this post is long but I hope it provided some useful background info on dreams.

www.lucidity.com

www.dreamresearch.net