Found an interesting article on how the brain works during sleep and the cause of REM(apologies if its been mentioned in the past):

http://www.harvardmag.com/issues/mj98/dream.html
extract:
"The dream gets accepted uncritically as reflecting reality because the dreamer's critical faculties lack the serotonin and norepinephrine they need for proper judgment. And the dream is mostly or entirely forgotten because this same chemical shortfall disables memory."

I found this bit at the end interesting... If it is true its interesting that we can gain such good dream recall and judgement within lucid dreams. Anyone have information on how lucid dreams and better dream recall through dream journaling fit into this?