Dreaming

Mental activity that takes place during sleep. It is thought to occur only during periods of REM (rapid eye movement) sleep, which last for about 20 minutes and occur 4–5 times a night. Compared to other phases, the REM phase of sleep is active. Blood flow and brain temperature increase, and there are sudden changes in heart-rate and blood pressure. Dreams usually closely mirror the day’s preoccupations. Dreaming can be seen as a process in which the mental impressions, feelings, and ideas are sorted out. People roused during REM sleep report especially vivid dreams.