Some scientists consider that dreams may just be side effects of chemical changes that represent the real purposes of the nervous activity in the brain, such as learning and consolidating memories. But, in spite of many scientific studies, the meaning of dreams is still a bit of a mystery. Researchers are generally in agreement that acetyl-choline (a powerful brain chemical) promotes dreaming and is implicated in memory consolidation during sleep. During the rapid eye movements period (REM) of sleep, which typically last 20 to 30 minutes, the sleeper is most likely to dream. Researchers believe that the dreams of REM promote a special kind of “emotional” learning, representing unconscious responses to recent, emotionally intense experiences. In sleeping brains nerve impulses are observed in cerebral areas concerned with vision, memory, attention, and thought. This activity involves consolidation of information learned during the day.