Sleep Cycles
One sleep cycle comprises of four stages and lasts for about 90-120 minutes. Dreams can occur in any of the four stages of sleep but the most vivid and memorable dreams occur in the last stage of sleep (also commonly referred to as REM sleep).
The sleep cycle repeats itself about an average of four to five times per night, but may repeat as many as seven times. Thus, you can see how a person can have several different dreams in one night. Most people, however, only remember dreams that occur closer toward the morning when they are about to get up.
But just because you can't remember those dreams does not mean that they never happened.
Some people swear on the fact that they simply do not dream, when in reality, they just don't remember their dreams.
Some books list four stages of sleep, while others say there are five stages. Some consider the first five-ten minutes when you are falling asleep as a stage in the sleep cycle. While other stages of sleep repeat themselves throughout the night, this phase of sleep does not.
