REM Sleep and DreamsMay 3, 2013
Although we spend a large portion of our lives sleeping, most of us know very little about what happens to our bodies while we slumber. For instance, did you know that there are four different stages of sleep? It's true. In fact, during each stage of sleep, your body and your brain have very distinctive changes.
These four stages make up what is called a "sleep cycle." Each sleep cycle lasts for approximately one and a half to two hours. This cycle repeats itself over and over again throughout the night. The longer you stay asleep, the less time it takes to go through the first three stages. In other words, you will reach stage four faster and faster during each rotation of your sleep cycle.
The Four Stages of Sleep Cycles
Sleep Stage 1
This occurs directly after you drift off and enter into a light sleep. In stage one, the body begins having: non-rapid eye movements (NREM), a decreased heart rate, a more relaxed musculature and a reduction in body temperature.
Sleep Stage 2
In this stage, you are completely asleep. Your body temperature drops even further as your immune system begins repairing damaged cells and removing harmful toxins. The endocrine glands release hormones and muscle tissue is restored.
Sleep Stage 3
Stage three is an even deeper sleep. Your metabolic (the regulator of the heart, lungs, intestines and the nervous system) levels have an extreme drop in during this stage.
Sleep Stage 4
This stage is the most regenerative part of sleep. Your blood pressure increases, respiration becomes inconsistent, your heart rate rises and your brain activity escalates. While in REM sleep, your eyes move randomly from side to side as if you're watching a tennis match with your eyes closed. Subconscious thoughts and hidden emotions may surface during this stage through your dreams.
The Dream Stage
The sleep cycle goes full circle approximately four or five times during the course of an eight hour sleep period. This explains why people frequently have multiple dreams in one night. For the most part though, people tend to only remember dreams that occurred shortly before they woke up.
Technically, you can dream in any stage of sleep. However, your most intensely real and unforgettable dreams emerge from the fourth stage, also known as the REM (rapid eye movement) or "dream stage." If you are awakened during this stage of sleep, you are more likely to vividly remember the particulars and details of your dreams.
REM sleep was first discovered and documented by Nathaniel Kleitman in 1953. Through his studies about sleep disorders, he was able to determine the way in which the neurons fire in a sleeping person's brain. Amazingly, Kleitman also discovered that during REM sleep the activity level in the brain was comparable to the levels of someone who is awake. This is why REM dreams can feel like they really happened. Some people even refer to REM dreams as "paradoxical dreams," because they can so closely mimic real life.