The Physiology of Sleep

I thought it would be a good idea for The Unlimited Dream Company to have a short article that summarized the facts about what the mind and body go through, objectively, during the sleep state. So this is the basic information, culled from various sources, listed at the end. I also include a couple of hints for dreamwork that make use of the activity of the mind/body.

Going to sleep

Using electroencephalogram (EEG) machines, which measure levels of brain activity, it has been seen that certain brainwave rhythms correspond to different modes of thought and activity.

Beta rhythms indicate that the mind is in an active state—this is our brainwave up until we decide to go to sleep. This mind state assesses and makes decisions.

On settling down to sleep, you gradually enter the alpha state. This is characterized by greater receptivity and fluidity in mental functioning. It is in this state that hypnagogic images can appear—those chaotic, often very vivid images that appear in such a half-conscious condition. It is also the state activated by Brion Gysin’s Dreamachine1 and other similar vision-inducing strobe/flicker devices.

Entering the sleep state

As your brainwaves slow, together with your physiological functions (slower heart rate & breathing, lower blood pressure), the first stage of sleep you enter is NREM—Non-Rapid Eye Movement—sleep. Dreaming does happen in NREM sleep, but flittingly and not in depth. Brainwaves will eventually sink to delta, deep sleep.

The first appearance of the second stage of sleep, REM sleep, is usually after about 90 minutes of sleep. REM sleep gives similar EEG readings to those of subjects who are awake; there is increased brain activity, the blood pressure and heart rate rise, with quicker, shorter breaths. It is during REM sleep that most dreams occur. It is accompanied in men by an erection and in women by increased vaginal blood flow.

REM sleep alternates with NREM sleep at intervals of approximately 90 minutes. You normally spend 20% of your sleep in dreams.

Re-arranging sleep

A few good techniques make use of these facts. One is to set your alarm to wake you up either 1.5, 3, 4.5, 6, etc. hours after going to sleep, so that you are woken up during a dream, to aid recall. Another is sleeping longer. About half of dreams occur in the last quarter of the sleeping period—and lucid dreams are more likely to happen in this final stage. By prolonging sleep, you obviously increase this final stage and increase your dreams and your chances of having lucid dreams.

Many may have had the experience of awaking in the morning from a dream, then drifting off back to sleep, usually dreaming more intensely, sometimes re-entering the same dream. A lot of great dreams are to be had in this way, and it is possible to re-arrange sleep to make use of the processes involved and increase dreaming if you haven’t got time to lie around in bed all morning. Simply…

  1. Set you alarm to wake you up about 2-3 hours earlier than usual.
  2. Get up when the alarm goes off! Don’t switch it off and have "five minutes" extra in bed. Get up and do all the things you need to do when you normally get up—breakfast, clearing up, reading mail/newspapers, etc. Stay awake for about 2 hours.
  3. Go back to sleep, and set the alarm for about 2 hours ahead. Dream.

This is actually a good technique even if you have got spare time when you wake up—I had my first lucid dream by doing this. You can play around with the timings to fit your own schedule. Instead of the usual 90 minutes between going to sleep and the first REM period, going to sleep soon after waking up only involves a few minutes in the transition phase—so you may get some good results from going back to sleep for as little as half an hour.

Sleep paralysis

During REM sleep, all muscles are paralyzed, except for respiratory functions and eyes. There may be slight muscle movements or twitches—these have been shown to correspond with movements made in the dream. Eye movements also correspond with movements made in the dream. Eye movements also correspond to the direction of sight in dreams (using this as a signal was how Stephen LaBerge objectively validated that a person could function in a conscious way in the dream state, dream lucidly).

The fact of sleep paralysis sometimes leads to terrifying episodes when the mind awakens but the body remains paralyzed. Whether the continuation of paralysis and waking is arbitrary and causes the terror, or the terror expressed in the dream causes the continued paralyzed state is a question whose answer will depend on the perspective you approach dreams from. The fact remains that the paralysis itself is quite natural and harmless, even if the consciousness of it is unusual and distressing. If you do awaken and find yourself paralyzed, just try to remember that no harm is being done and it will pass in a couple of minutes. Alternatively, you could utilize this state:

Sleep paralysis is not only nothing to be frightened of, it can be something to be sought after and cultivated. Whenever you experience sleep paralysis you are on the threshold of REM sleep. You have, as it were, one foot in the dream state and one in the waking state. Just step over and you’re in the world of lucid dreaming.

Stephen LaBerge

When you awaken from a dream, relax yourself completely—an easy way of doing this is to progressively tense and relax each muscle group (feet, calves, thighs, etc.). Each time, feel the tension as you breath in, then imagine and feel its release as you breath out. As you fall back to sleep, affirm to yourself that you will re-enter the dream state consciously. Mentally observe body as it enters REM paralysis (remember it only takes the brain a few minutes to enter REM sleep after waking up for a while). Signs of the onset of REM sleep are: strange vibrations in the body, feelings of electrical currents passing through parts of the body, distortions in body image. When you feel the body to be completely paralyzed, attempt to release the dream body from the physical body. Move your dream body out of the bed, roll out of your physical body, try flying… Each person will find their own ‘knack’. You are then in the dream, lucid.


  1. A cardboard cylinder, with slits, placed on a turntable with a light source in the middle. The slits and speed of the turntable are arranged so that the light flickers on the user’s closed eyes at about the same rate as alpha waves, inducing colourful patterns and inner visions. [back to text]


  • Exploring The World Of Lucid Dreaming by Stephen LaBerge & Howard Rheingold (Ballantine, 1990)
  • The Power Of Your Dreams by Soozi Holbeche (Piatkus, 1991)
  • Dreamachine Plans created by Brion Gysin (Temple Press, 1992)
  • The Innocence Of Dreams by Charles Rycroft (Hogarth Press, 1991)