Sleep and Dreams, are the two states of which we know precious little.

Sigmund Freud, in his attempt to interpret the Dreams, has set up a system of Psychiatry, blames every one for their actions but themselves.

He had interpreted Dreams only as an expression of Sex and depressed desires.

Jung professed ‘Freud conceived the unconscious solely as a repository of repressed emotions and desires. Jung agreed with Freud’s model of the unconscious, what Jung called the “personal unconscious“, but he also proposed the existence of a second, far deeper form of the unconscious underlying the personal one. This was the collective unconscious, where thearchetypes themselves resided, represented in mythology by a lake or other body of water, and in some cases a jug or other container. Freud had actually mentioned a collective level of psychic functioning but saw it primarily as an appendix to the rest of the psyche’

Then we have many Behavioral Psychologists.

These scholars saw Mind as a Blind seeing An Elephant” seeing a part and interpreting it to suit them.

Patanjali goes to the basics.

Since we do not remember anything in sleep, is Sleep ‘Absence of Thoughts?’

He says NO.

According to Yoga Sutra 1.10, Sleep is a State where one is not aware of the thought waves.(Deep Sleep)

This can not be confused with the ‘Yoga Sate where one is devoid of Thought waves”

‘Abhava pratyaya Alambana vritti Nidra” Yoga Sutra 1.10

‘

abhāva – absence, non-existence, nullity
pratyaya – cause, resulting impressions
ālambanā – support, basis, foundation, cause
vṛttiḥ –  habits or activities of the mind
nidrā – deep sleep

Translation

“Sleep is the mental habit characterized by the absence of form”

That is we are not ascribing, in the Deep sleep stage,a Form for the Thought waves, that’s all.

Indian Philosophy characterizes Four stages of Sleep.

1.Wakefulness, Jagruti.

2.Swapna,Dream State

3.Sushupti,Deep Dreamless State and

4.Thuriya, The Real Nature of Brahman,Pure Consciousness.

”

Adi Shankara discerned three states of consciousness, namely waking (jågrat), dreaming (svapna), and deep sleep (suƒupti),^{[web 61][web 62]} which correspond to the three bodies:^[140]

1. The first state is the waking state, in which we are aware of our daily world. “It is described as outward-knowing (bahish-prajnya), gross (sthula) and universal (vaishvanara)”.^{[web 62]} This is the gross body.
2. The second state is the dreaming mind. “It is described as inward-knowing (antah-prajnya), subtle (pravivikta) and burning (taijasa)”.^{[web 62]} This is the subtle body.
3. The third state is the state of deep sleep. In this state the underlying ground of concsiousness is undistracted, “the Lord of all (sarv’-eshvara), the knower of all (sarva-jnya), the inner controller (antar-yami), the source of all (yonih sarvasya), the origin and dissolution of created things (prabhav’-apyayau hi bhutanam)”.^{[web 62]} This is the causal body.

A fourth state is Turiya, pure consciousness. It is the background that underlies and transcends the three common states of consciousness.^{[web 63] [web 64]} In this consciousness both absolute and relative, Saguna Brahman and Nirguna Brahman, are transcended.^[141] It is the true state of experience of the infinite (ananta) and non-different (advaita/abheda), free from the dualistic experience which results from the attempts to conceptualise ( vipalka) reality.^[142] It is the state in which ajativada, non-origination, is apprehended.^[142](Wiki)

What does Modern Science say on this?

Stage 1

Stage 1 is the beginning of the sleep cycle, and is a relatively light stage of sleep. Stage 1 can be considered a transition period between wakefulness and sleep. In Stage 1, the brain produces high amplitude theta waves, which are very slow brain waves. This period of sleep lasts only a brief time (around 5-10 minutes). If you awaken someone during this stage, they might report that they weren’t really asleep.

Stage 2

Stage 2 is the second stage of sleep and lasts for approximately 20 minutes. The brain begins to produce bursts of rapid, rhythmic brain wave activity known as sleep spindles. Body temperature starts to decrease and heart rate begins to slow.

Stage 3

Deep, slow brain waves known as delta wavesbegin to emerge during stage 3 sleep. Stage 3 is a transitional period between light sleep and a very deep sleep.

Stage 4

Stage 4 is sometimes referred to as delta sleepbecause of the slow brain waves known as delta waves that occur during this time. Stage 4 is a deep sleep that lasts for approximately 30 minutes. Bed-wetting and sleepwalking are most likely to occur at the end of stage 4 sleep.

Stage 5

Most dreaming occurs during the fifth stage of sleep, known as rapid eye movement (REM) sleep. 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, muscles become more relaxed. Dreaming occurs due because of increased brain activity, but voluntary muscles become paralyzed.

The Sequence of Sleep Stages

It is important to realize, however, that sleep does not progress through these stages in sequence. Sleep begins in stage 1 and progresses into stages 2, 3 and 4. After stage 4 sleep, stage 3 and then stage 2 sleep are repeated before entering REM sleep. Once REM sleep is over, the body usually returns to stage 2 sleep. Sleep cycles through these stages approximately four or five times throughout the night.

On average, we enter the REM stage approximately 90 minutes after falling asleep. The first cycle of REM sleep might last only a short amount of time, but each cycle becomes longer. REM sleep can last up to an hour as sleep progresses.

http://psychology.about.com/od/statesofconsciousness/a/SleepStages.htm

http://ramanisblog.in/2013/04/21/how-to-communicate-words-patanjali-yoga-1-9/

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