Dreaming and sleep cycles
When do dreams occur? This is a very common question that is often raised about dreams. Some people mistakenly believe that dreaming takes place when the individual exhibits a restless state, such as when he is tossing and turning in his bed, or when is grinding his teeth, and when he is sleepwalking. The truth is these occurrences do not automatically signify the onset of of the dreaming state. In fact, when an individual is dreaming, his muscle tone actually relaxes though his heart rate and blood pressure have been noted to rise up.
One of the most reliable indicators that an individual has entered the dreaming state is the occurrence of rapid eye movement. Rapid eye movement refers to the sudden and continuous movement of the eyeballs while asleep. The occurrence of rapid eye movement is so distinguishable and significant in determining the mental and cognitive processes that are going on in the sleeping person’s head that the various stages or sleep cycles are actually built around it. We thus have two basic sleep cycles: the non-rapid eye movement sleep (NREM) and the rapid eye movement sleep (REM). The NREM cycle is further subdivided into three stages while REM sleep is generally considered as a single stage.
Most dreaming occurs during REM sleep, when the body and mind is at its most conducive state for dreaming. While in REM sleep, adrenaline levels increase while the body’s muscles enter a state of REM atonia wherein they are almost paralyzed and their sensitivity to external stimuli is very low. When a person is in REM sleep, it is generally very difficult to wake him up although persistent efforts may be successful. If one is awaken while in the middle of REM sleep, he will have a vivid recollection of the dream he was having.
For a long period of time, it was thought that dreams only occur during REM sleep. More recent studies, however, have revealed that dreams can also occur during stage 3 of the NREM cycle. These dreams, however, occur sparingly and most dreams are still seen to be largely concentrated in REM sleep.
So when exactly does dreaming occur? The correct answer would be that it generally occurs during REM sleep, or in some instances during stage 3 of the NREM cycle immediately before one enters REM sleep. In real time, dreaming can begin anytime between 30 to 90 minutes after falling asleep. Dreams may last up to around 45 minutes and end when the individual reenters the NREM cycle. Dreaming occurs more than once during a single sleep period which usually contains around 4 to 7 intervals of REM sleep.
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