Dream research remains in its infancy in the West, having only recently acknowledged lucid dreaming, but mostly from a modern materialist perspective. To date researchers have mapped four main brain states, though there may be others that current equipment can not yet detect:

1. Beta ~ 14-100 cycles per second, normal alert waking state. Higher range associated with anxiety, dis-ease, fight or flight conditions.

   » Gamma �?a subset of Beta, 40 cycles per second, but range from 24 to 70 cycles per second. Associated with an alert waking state, these have been found in meditative and lucid dreaming (REM) states. (Included as a subset because they are assoicated with a sense of clarity and wakefulness in the brain and mind, even though the rest of the body may be in a sleep, meditative, or trance state.)

2. Alpha ~ 8-13.9 cycles per second, just below the normal state of alertness. Associated with light relaxation, daydreaming, and self-reflection. A non-drowsy, yet relaxed, tranquil state of inward awareness that occurs before sleep. Beginning access to subconscious mind.
3. Theta ~ 4-7.9 cycles per second, deep relaxation, reverie, lucid dreaming, mental imagery, meditation, increased memory and focus, deep-rooted memories, and inspiration. Characterized mainly by light sleep, rapid eye movement (REM) dreams, and hallucinations. Hypnogogic imagery, deep meditation, access to subconscious mind.
4. Delta ~ .1-3.9 cycles per second, the deepest, most rejuvenating stage of dreamless, non-REM sleep and deep meditation. It also produces stress reduction, which can promote healing of the body. Human growth hormones released and loss of body awareness.

http://www.newworldview.com/library/Helfrich_P_Glossary.html#Aspect_Psychology