What is REM Sleep? - Definition & Explanation

Instructor: Gary Gilles

Gary has a Master's degree in Counseling Psychology and has been teaching and developing courses in higher education since 1988.

Rapid eye movement (REM) is the deep, restorative sleep stage in which dreams occur. Explore the characteristics and behavior of REM sleep, the four stages of sleep, the importance of REM sleep, and what can interfere with it. Updated: 02/05/2022

What is REM Sleep?

Did you know there is a lot going on in your mind and body when you are asleep? It's true. You may not be aware of it, but your brain cycles through five different stages of sleep several times every night. REM sleep is the fifth and arguably the most important of those stages.

REM sleep helps renew your mind and plays an important role in your ability to learn and remember. Without adequate REM sleep, even for one night, you are likely to feel tired the next day and not function at your optimal level. To better understand REM sleep, let's briefly take a look the first four stages of sleep and what happens in each stage.

The Five Stages of Sleep

Stage 1 is what you experience just as you are drifting off to sleep. Some people call it the twilight stage because you are still somewhat aware of your surroundings. This stage of very light sleep typically lasts about five minutes.

During stage 2, your sleep is a little deeper but it is still light. If you hear a slight noise while in stage 2 you would easily wake up. Stage 2 sleep lasts about 45-50 minutes.

It is during stage 3 that you begin to fall into a deeper sleep, but this is a transition phase and only lasts about five minutes.

In stage 4 you experience your deepest sleep, and it may be difficult for you to be awakened when you are in this stage. It lasts about 15 minutes.

It takes about 70-90 minutes to pass through these first four stages of sleep. Each stage is a continuous progression toward stage 5 or REM sleep, which lasts about 25 minutes. Including REM, a complete sleep cycle takes 90-110 minutes, and most people go through four to six complete cycles per night. Ideally, time in REM sleep should get progressively longer with each cycle as the amount of time spent in deep sleep (stage 4) decreases.

Dreaming and REM Sleep

REM is also the stage where you do most of your dreaming. If you've ever watched someone in REM sleep you would notice that their eyes, though closed, are moving back and forth rapidly as they dream. This is how REM sleep gets its name. REM stands for rapid eye movement, and this movement of the eyes is your mind's way of processing dreams you are experiencing.

Your Body in REM Sleep

When you move into REM sleep, your body reacts differently than in any of the other sleep stages. Your:

• breathing become more rapid and shallow

• limbs no longer respond to voluntary control

• blood pressure rises

• heart rate increases

During REM sleep, your brain is organizing and processing the information you learned during the day. The brain is also hard at work making new nerve connections, healing tired muscles, strengthening your immune system and restoring your supply of mood-boosting chemicals such as dopamine and serotonin.

REM Sleep Thieves

Certain foods, beverages and medicines can affect how the brain and body work together to help you sleep. Some of the most common REM sleep disruptors are listed below.

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