This suggests that dreams serve an important function in our lives. The light sleep that occurs just after dozing off is called Stage 1 sleep. People are easily awakened during Stage 1 sleep and often do not realize they have been sleeping. Stage 1 sleep normally lasts only a few minutes. Stage 2 sleep follows and is a deeper level sleep.
Eye movements are minimal and muscular activity decreases to an even lower level.
Brain wave activity known as the K-complex can occur and is in response to an external stimulus, like the sound of a voice or an internal stimulus like stomach cramps. This cycle progresses into an even deeper Stage 3 level sleep characterized by delta waves. When these waves account for 50 percent of the EEG tracing, a person is in Stage 3 sleep. When delta waves exceed 50 percent in proportion to other brain waves, the subject is in Stage 4 sleep, the deepest level of sleep. It is difficult to awaken someone from Stage 4 sleep, and if they are awakened, they will be disoriented and confused.