Deep Sleep, continued

Earlier article: The Advaita-Vedanta fascination with Deep Sleep

The four states in traditional Vedanta are: Waking, Dreaming, Deep Sleep, and the Fourth state (Turiya).  They are talked about in various Upanishads.

From the Wikipedia entry on Turiya

Turiya is discussed in Verse 7 of the Mandukya Upanishad; however, the idea is found in the oldest Upanishads. For example, Chapters 8.7 through 8.12 of Chandogya Upanishad discuss the "four states of consciousness" as awake, dream-filled sleep, deep sleep, and beyond deep sleep.  Similarly, Brihadaranyaka Upanishad, in chapter 5.14 discusses Turiya state, as does Maitri Upanishad in sections 6.19 and 7.11. 

Verse VII of the Mandukya Upanishad describes Turiya:

Not inwardly cognitive, nor outwardly cognitive, not both-wise cognitive,
not a cognition-mass, not cognitive, not non-cognitive,
unseen, with which there can be no dealing, ungraspable, having no distinctive mark,
non-thinkable, that cannot be designated, the essence of assurance,
of which is the state of being one with the Self
the cessation of development, tranquil, benign, without a second,
such they think is the fourth. He is the Self (Atman). He should be discerned.

Not content with asserting the state of Turiya, some minor Upanishads talk about a fifth state, Turiyatita (the state beyond Turiya):

II.4. There are five AvasthA-s (states): jAgrat (waking), svapna (dreaming), suShupti (dreamless sleeping), the turIya (fourth) and turyatita (that beyond the fourth)...

II.5. The Yogin is one that has realised Brahman that is all-full beyond turIya.

(Mandala Brahmana Upanishad, Translated by K. Narayanasvami Aiyar)

Search the texts and the internet, talk to the sages and the gurus, discuss it with Vedantin monks or seekers,  and here is what you will find.

What to talk of the fourth and the state beyond the fourth, only a rare few have so much as experienced some consciousness during deep sleep (though they might tell you about vivid dreaming, and awareness during light sleep, and awareness of when they fall asleep).  The states of Turiya and the even more transcendent state of Turiyatita are seemingly just fanciful concepts, having absolutely no counterpart in human experience.

One has to just read some of the things people say about "awareness during deep sleep" to see what tosh it all is, in their conception of it as a spiritual or mystical phenomenon:

In fact, even the apparent fact that deep sleep lasts for a period of time, say for four hours, is a superimposition in the mind’s own terms onto something called ‘deep sleep,’ in which, by definition, time is not present. Therefore, deep sleep does not last in time.

As scientists continue to study sleep and brain rhythms, there is some initial fringe research which is now questioning whether some form of consciousness can still persist even in what traditionally is dreamless sleep:

The third category is a "selfless" state of sleep. The researchers said that this state not only involves dreamless sleep, but also a certain amount of conscious awareness on the part of the person that he or she is sleeping. This state may be similar to the experiences of Indian and Tibetan meditators, the researchers said. They suggested that people who are skilled at meditation are more likely to experience this third state, but more research is needed before scientists can tell whether or not this is true. 

Calling it "selfless" is disingenuous.  Of course if the person is aware that "he or she is sleeping" that it is not really a disembodied awareness, but one that is firmly rooted in the body.  One might be totally oblivious to sense experiences, but still somewhat aware internally and have a very, very mild and soft-spoken inward dialog.

But more pertinently, there is nothing "spiritual" about this awareness.  Of course the brain is not dead during sleep, so some minor waves might still exist which can, perhaps in a suitably trained individual, make him or her somewhat aware of even dreamless sleep.  What is so mystical about it?  How can someone say that "time is not present".  Just because oneself is not totally aware of what is going on, does not mean that the outside world is no more.