Stages of Sleep

By Diana L. Walcutt, Ph.D

Do you ever wonder why you don’t dream when you sleep? The truth is, if you are getting proper amounts of sleep in proper time periods, and not taking medications or using alcohol or illegal substances, you are dreaming. You just don’t remember them unless they wake you.

Stages of Sleep

Wakefulness includes Gamma, High Beta, Mid Beta, Beta Sensory Motor Rhythm, Alpha, and Theta brain waves. Our composite brain wave, that is, what you would see if you had an EEG (electro-encephalo-graph, or picture of the electrical activity in your brain), would be made up of many of the brain waves named above, all at the same time.

Stage One

When we are preparing to drift off, we go though Alpha and Theta, and have periods of dreaminess, almost like daydreaming, except we are beginning to fall asleep. These are interesting states, in that we experience them throughout the day and some people may have more of these waves than others.

Those who practice meditation, or deep prayerfulness, often kinda “hang out” in Alpha. It’s a restful place. During this stage, it’s not unusual to experience strange and extremely vivid sensations or a feeling of falling followed by sudden muscle contractions. These are known as hypnogogic hallucinations. You may even feel like you are hearing someone call your name, or the phone ringing. Recently, I thought I heard the doorbell, but realized that it was a hypnogogic hallucination and went back to sleep.

We then begin to enter Theta, which is still a relatively light period between being awake and asleep. This usually lasts for 5-10 minutes. Research has shown that the average sleeper takes about 7 minutes to fall asleep. You may fall asleep sooner, or take longer.

Stage Two

The second stage of sleep lasts about 20 minutes. Our brain begins to produce very short periods of rapid, rhythmic brain wave activity known as Sleep Spindles. Body temperature begins dropping and heart rate starts slowing down.

Stage Three

Deep, slow brain waves known as Delta Waves begin to emerge during this stage. It is a transitional period between light sleep and a very deep sleep.

Stage Four

This is sometimes referred to as Delta Sleep because of the delta waves that occur during this time. Stage Four is a deep sleep that lasts for about 30 minutes. Sleepwalking and bed-wetting typically happen at the end of Stage Four sleep. (This does not include the problems that can happen with sleep medications like Ambien and Lunesta).

Stage Five: REM

Most dreaming occurs during Stage Five, known as REM. REM sleep is characterized by eye movement, increased respiration rate and increased brain activity. REM sleep is also referred to as paradoxical sleep because, while the brain and other body systems become more active, your muscles become more relaxed, or paralyzed. Dreaming occurs because of increased brain activity, but voluntary muscles become paralyzed. Voluntary muscles are those that you need to move by choice, for example, your arms and legs. Involuntary muscles are those that include your heart and gut. They move on their own.

Rapid eye movement, or REM sleep, is when you typically dream. You may have images float by in earlier stages, particularly when you are going through Alpha or Theta, but the actual dream state occurs in REM.

This period of paralyzation is a built-in protective measure to keep you from harming yourself. When you are paralyzed, you can’t leap out of bed and run. Do you ever feel like you can’t escape during a dream? Well, the truth is, you can’t. You can breathe, and your heart is working, but you really can’t move.

Cycles

Sleep does not progress through all of these stages in sequence, however. Sleep begins in Stage One and progresses into stages 2, 3, and 4. Then, after Stage Four sleep, Stages Three, then Two are repeated before going into REM sleep. Once REM is over, we usually return to Stage Two sleep. Sleep cycles through these stages approximately 4 or 5 times throughout the night.

We typically enter REM approximately 90 minutes after falling asleep. The first cycle of REM often lasts only a short amount of time, but each cycle becomes longer. This is why we need long periods of sleep each night. If we get short periods of sleep, we can’t really get through the stages we need to heal and stay healthy. REM can last up to an hour as our sleep progresses. In case you are wondering, if you feel like a dream is taking a long period of time, it really is. Contrary to what was once believed, dreams take as long as they actually seem.

Getting sleepy? OK, sleep well, perchance to dream….

 

APA Reference
Walcutt, D. (2009). Stages of Sleep. Psych Central. Retrieved on September 20, 2014, from http://psychcentral.com/lib/stages-of-sleep/0002073
Scientifically Reviewed
    Last reviewed: By John M. Grohol, Psy.D. on 30 Jan 2013
    Published on PsychCentral.com. All rights reserved.