By reading the chapter 5, the most interesting concept for me is the stages of sleep. Do you think mostly the time of sleeping occur in olny a few mintues? Even, you can't distinguish dream and reality when you wake up. But actually, we experience five stages and each cycle lasts about 90 minutes,thereinto REM sleep is fifth stage in our sleeping and REM means rapid eye movement (Aserinsky and Kleitman,1953) and many REM are emotional, illogical, nd prone to sudden shifts in"plot (Foulks,1962;Hobson,Pace-Schott,&Stickgold,200). In contrast, Non-REM tend to real life and it is shorter.
I just found an interesting video about a sleeper has REM. It seems that the brain of the sleeper is acting actively. I think it is very amazing, we don't have any feelings about our body behaviors during sleeping, I can't image it is truth that my eyes are still moving while I am sleeping. Anyway I believe sleeping is an indispensable and significantly behavior during our life.