In Hinduism, both relaxation training and lucid deep sleep are called yoga nidra. There are various yogis that teach the former, few produce students that can maintain long periods of delta brain waves associated with deep sleep while being able to report events during that period, with conscious awareness. As we shall see, this is a functional definition of lucid deep sleep, and this is the variety of nidra yoga that we are addressing here.
In this practice awareness exists during deep, dreamless sleep, of the physical environment as well as the self, with its thoughts, feelings, and emotions, without content or differentiation. There is no perception of, because there is no longer a distinction between knower and known, perceiver and the perceived. Instead, there is clear, formless awareness, called turiyatita in Sanskrit. References to trance to describe lucid deep sleep are unnecessary because they imply ordinary waking consciousness has been put to sleep or suspended, as in shamanic journeying, which is not the case. In lucid deep sleep waking consciousness is present, only shifted into “neutral,” or functioning in a non-typical way. Similarly, it is not necessary to appeal to the operation of an unconscious or superconscious, because both imply the occurrence of something other than lucidity by waking consciousness. These are distractions from the central point of nidra yoga, that waking identity is lucid during deep sleep.
Two Accounts of Lucid Deep Sleep
In 1971, at the Menninger Foundation in Kansas City, researchers under the direction of Elmer Green used an electroencephalograph (EEG) to measure brain wave states of an Indian guru and adept, Swami Rama. He demonstrated the ability to generate different brain wave states at will, including the slow and low amplitude delta waves associated with deep sleep. “Imagining an empty blue sky with occasional drifting clouds” produced alpha waves, reflecting a state of deep relaxation that is differentiated from the beta waves normally associated with waking consciousness. Production of theta waves, correlated with dream sleep, was produced by the swami by “stilling the conscious mind and bringing forth the subconscious,” which he did for 75% of the 5 minute test period. Then “…the swami entered the state of (usually unconscious) deep sleep, as verified by the emergence of the characteristic pattern of slow rhythm delta waves. However, he remained perfectly aware throughout the entire experimental period. He later recalled the various events which had occurred in the laboratory during the experiment, including all the questions that one of the scientists had asked him during the period of deep delta wave sleep, while his body lay snoring quietly.”
A second account, reported by Ken Wilber, partially takes lucid deep sleep out of the province, vocabulary, and conceptual framings of Hinduism. “….At some point in the evening we got into a discussion about meditation and the changes it can produce in brain waves. A young man training to be a psychiatrist asked me to get out a videotape I have of me connected to an EEG machine while I meditate. He believed none of the discussion about how meditation could profoundly alter brain waves, and he wanted ‘proof.’
The tape shows me hooked to an EEG machine; this machine shows alpha, beta, theta, and delta waves in both left and right hemispheres. Alpha is associated with awake but relaxed awareness; beta with intense and analytic thinking, theta is normally produced only in the dream state, and sometimes in states of intense creativity; and delta is normally produced only in deep dreamless sleep. So alpha and beta are associated with the gross realm; theta with the subtle realm; and delta with the causal realm. Or, we could say, alpha and beta tend to be indicative of ego states, and delta of spirit states. Delta presumably has something to do with the pure Witness, which most people experience only in deep dreamless sleep.
This video starts with me hooked up to the machine; I am in normal waking consciousness, so you can see a lot of alpha and beta activity in both hemispheres. But you can also see a large amount of delta waves; in both hemispheres the delta indicators are at maximum, presumably because of constant stable witnessing. I then attempt to go into a type of nirvikalpa smadhi — or complete mental cessation — and within four or five seconds, all of the machine’s indicators go completely to zero. It looks like whoever this is, is totally brain-dead. There is no alpha, no beta, no theta–but there is still maximum delta.
After several minutes of this, I start doing a type of mantra visualization technique — yidam mediation, which I have always maintained is predominantly a subtle-level practice–and sure enough, large amounts of theta waves immediately show up on the machine, along with maximum delta. The fact that theta, which normally occurs only in dreaming, and delta, which normally occurs only in deep sleep, are both being produced in a wide-awake subject tends to indicate a type of simultaneous presence of gross, subtle, and causal states (e.g., turiyatita). It is, in any event, attention-grabbing.” 
Understanding Lucid Deep Sleep
The central point, that lucid deep sleep is formless, content-free, focused and deeply relaxed clear awareness, is extremely important to remember in order to keep yourself from getting confused about what it actually is. Otherwise, you will obscure lucid deep sleep with various cultural practices and assumptions that have come to be associated with it. Examples include the repetition of Sanskrit mantras, the use of singing bowls, various other forms of yoga, and creative visualization. Richard Miller, a teacher of Yoga Nidra in the U.S., teaches a process of moving through the koshas, or energy sheaths, or finer energy bodies in order to reach the innermost layer of innate joy and peacefulness. Desensitization, body scanning, focus on the “third eye,” and objectification of the thinking, feeling, sensing “I” are other practices you may encounter among those who teach nidra yoga. Examples of assumptions that often accompany descriptions of nidra yoga include karma, the unconscious mind, transcendental consciousness, stress reduction, cleansing, integrating the left and right hemispheres of the brain, logical and “intuitive” perspectives, “store consciousness,” sat, cit, ananda, reactivation of the pineal gland and its production of melatonin, the “field of conscious, pranic intelligence,” communion with the divine, psychic abilities, or a shamanic awareness of other planes of existence. One must also beware of concluding that because lucid deep sleep is associated with delta brain wave patterns that it is an epiphenomenon, or reducible to physiological processes. All of these practices and assumptions add practical and theoretical scaffolding that is intended to support and clarify, but which does not exist in lucid deep sleep itself. Such assumptions are attempts to describe what formless, relaxed, clear awareness is. Once it is laboriously constructed and maintained, all that scaffolding has to be deconstructed, if you are to experience a formless, contentless state of awareness during deep sleep.
Lucid Deep Sleep as Formless Meditation
We can be relatively sure that lucid deep sleep is a byproduct of forms of meditation that involve both relaxation and an ability to maintain focused awareness without content. We can observe this understanding in Wilber’s account above, when he notes the presence of delta waves in normal waking awareness, accompanying beta and alpha waves, and indicating a cultivation of formless witnessing in everyday mind through regular and deep meditation.
What does a formless practice of meditation look like? Preliminary skills are relaxation and focus. The techniques that you use to learn to relax and focus are arbitrary, and every school claims its practices are the most effective. However, these generally involve either visualization, mental repetition, simple observation, or some version of the via negativa, neti, neti, “not this, not this,” as in the naming of the objects of awareness. Experiment with various methods from different schools, because you will find that each adds something to the depth of your relaxation and your ability to maintain focus. Variation is good, but consistency of practice is most important.
Just as in the mastery of lucid dreaming, variety and consistency of repetition of core competencies of relaxation and focus improves the likelihood of success. The more relaxed you become the more you mimic the deep sleep state; the more focused you become the more you acquire the ability to take alert and clear awareness into the deep sleep state. Consequently, working relaxation and focus into your everyday mind increases the likelihood you will practice them in your dreams, lucid dreams, and deep sleep. In order to do so, four half an hour periods of practice a day are more effective than one two-hour period, because repetition throughout the day is more impactful for the cultivation of awareness in both dream and sleep states. Approach your practice as if you were training for a marathon. First develop your endurance by building up your ability to simply sit in meditation, zen-style, for some extended period of time, say two hours. Once you have developed simple physical and mental endurance, you need to learn how be both profoundly relaxed yet awake, aware, and focused at the same time. This is because these competencies are necessary pre-requisites to lucid deep sleep. Deep, regular, daily periods of mediation program you to move into a state of clear, relaxed, focused awareness whenever you want until it becomes your habitual, everyday mind. This does not mean you stop eating, thinking, working, and feeling, and has nothing to do with purification as either a goal or a necessary preparation. Lucid deep sleep is not a trance state nor is it a matter of “dropping” your everyday mind. Instead, you are expanding it. You do so until you can easily access contexts that are formless, that is, they transcend, yet include, all possible content. Whatever comes up exists within the context of relaxed, focused, clear awareness, like the earth and all its life existing within the context of the sky, or like the earth and sky existing within the content of timeless, dimensionless space, or like space existing within the context of all possible universes.
Because most of us associate relaxation with sleep and sleep with unconsciousness, practicing meditation lying down invites sleep, and deep sleep is not meditation; it is unconsciousness, except for experienced meditators. Therefore, it is wise to take on practices that support attention, awareness, and focus. These include sitting, walking, or working while meditating, keeping your eyes open, and one or more of the above-mentioned tools (visualization, mental repetition, simple observation, or some version of neti, neti) until they are no longer required in order for you to maintain relaxed, open awareness, even when lying down. Because the repetition of a mantra, syllable, sound, or verse tends to encourage trance, a state in which your waking mind is no longer present, aware, and engaged, Integral Deep Listening encourages the simple naming of whatever arises into your awareness. This requires the alert presence of consciousness while teaching it to remain so in the spaces between the arising of contents of awareness.
Steps for Learning Lucid Deep Sleep
There exists a natural four-step process for learning lucid deep sleep. First practice formless, clear, focused, and relaxed varieties of meditation while awake, then while dreaming, then while lucid dreaming, and finally during deep sleep. While all of these can be practiced concurrently, awakening in the outer states increases the likelihood of success with attempts at lucidity while deeply asleep. Therefore, lucid deep sleep becomes much more likely the more the above three steps are followed. Conversely, it is precisely the absence of such meditative practice from the lives of most individuals that makes spontaneous occurrences of lucid deep sleep, let alone regular experiences of deep sleep lucidity, unlikely.
Does Lucid Deep Sleep Imply Enlightenment?
Nidra yoga is a dream yoga in the same way that waking is a dream state: waking up in either is a movement from relative unconsciousness into relative awareness and clarity. Lucid deep sleep is both a form of meditation and meditative consciousness itself. Once learned, this meditative consciousness can co-exist within waking, dreaming, lucid dreaming and deep sleep states. Lucid deep sleep is a clear, simple, direct practice of waking up, a skill that requires the pre-existence of non-typical degrees of relaxation and focus at the same time. Notice that it does not imply anything else. Just as anyone can lucid dream, so anyone who masters formless meditation can experience lucid deep sleep. Being able to be deeply relaxed yet focused at the same time does not imply that you are psychic, enlightened, holy, one with God, in a state of constant bliss, unusually ethical, balanced, intelligent, or rational. The self can achieve strong mental focus and deep relaxation without requiring development of other lines. The paradigm for this is wizardry, whether white or black. For example, some yogis, considered enlightened masters, and probably quite capable of lucid deep sleep, have been physically unhealthy, weak, and fat; others have been pedophiles or alcoholics. Therefore, be careful and cautious about assumptions you make about your own level of development or that of those who learn lucid deep sleep. One mark of confidence is the ability to err on the side of humility.
The Paradox of Lucid Deep Sleep
From the standpoint of the self, more consciousness is better, because it means more awareness, more control, more freedom, more power, more capability, and more growth. However, the perspective of the self is not the only point of view, worldview, context, or perspective that exists or that needs to be considered. For one, there is the perspective of life itself. To assume that the two are the same, that the priorities of life must or will coincide with those of the self, is a reflection of psychological geocentrism. Because reality revolves around the self and its worldview, life’s priorities must be in agreement. Are they? How do you know? Setting waking up or enlightenment as a life goal can easily imply an aversion to, conflict with, and minimization of, unconsciousness. This is a massive and fatal assumption, in that it puts the self in conflict with life. In such a conflict, guess who wins? The only way to know the priorities of life and then to determine whether or not they are in conflict with those of the self, is to suspend the priorities of the self and, to the best that we can, view life from the perspective of life itself. While this is impossible, because subjectivity can never be eliminated, it can be reduced, and IDL dream yoga is one way to do so. The fact that such interviews can indeed put you in contact with the priorities of life is based on the eliciting of perspectives and recommendations that do not reflect those of the self.
Two of these priorities are involution and unconsciousness. Life spends a great deal of time and energy being unaware. Why? Is life stupid? Are we smarter than life itself? The desire for consciousness during deep sleep may imply an affirmation of the belief that consciousness is better than unconsciousness and that wakefulness is better than deep sleep, lack of awareness, and death. It may equate freedom, liberation, and enlightenment with constant awareness and wakefulness, while bondage, enslavement, and delusion are assumed to be characteristics of unawareness and deep sleep. Does life itself demonstrate any of these preferences? While evolution is a process of awakening, involution is a process of moving into deep and complete unconsciousness. Which is more important, evolution or involution, awakening or unconsciousness? Is yang more important than yin? What are the implications of setting one half of reality in conflict with the other half? Is doing so supportive of the agenda of life?
Another example of how the self easily puts itself into conflict with life is the concept of expansion. Everyone wants to expand his or her consciousness. By this they mean to become smarter, wiser, more inclusive, empathetic, loving, accepting, peaceful, and good. What about contraction? Is inhalation, or the expansion of the lungs and the taking in of oxygen “better” than the contraction of exhalation? Is this the perspective of life or only of the self when it values evolution, expansion, and consciousness over involution, contraction, and unconsciousness? Is it wise to imagine that life is at war with itself, with one half being “good” and the other “bad?” Is this not essentially the position of both shamanism and manichaeistic dualism? Is it not based on repression and fear?
A larger context includes and balances both, creating a place for greater unconsciousness, rest, imbalance, attachment, limitation, confusion, fear, self-concern, unknowingness, rejection, stress, and subjectivity. If these are indeed priorities of life as well, then deep sleep will always have a respected and necessary place in life; it will never be outgrown. If our desire is to align with life’s priorities, through accessing and following our life compass, then we need to honor deep sleep for its own sake, as a fountain of emptiness and formless creativity, instead of setting a goal of becoming awake and aware at all times. The crucial distinction is between gaining the ability to be conscious, so that we have the choice whether or not to be so in any state, as opposed to needing to be conscious at all times.
Lucid Deep Sleep as a Stage in the Evolution of Life
Because the degree of brain activation during dream sleep is similar to waking, researchers have referred to dreaming as “paradoxical sleep.” Some have theorized that dreaming is an evolutionary adaptation that maintains arousal and vigilance during periods of regeneration, recuperation, and assimilation. Just as lucid dreaming is an evolutionary advance in wakefulness within the state of dream sleep, so lucid deep sleep is an evolutionary advance in wakefulness within the state of deep sleep. Just as waking awareness centers on the evolution of the self, so dreaming is evolution of a multi-perspectival, collective identity that transcends and includes any and all definitions of self. In comparison to both waking and dreaming, deep sleep is evolution of life as unified consciousness. In each of these three states there is a movement from unconsciousness to clear awareness, and a developmental sequence indeed exists: waking enlightenment or lucidity makes dream lucidity more likely, and both make deep sleep lucidity more likely. This does not mean that dream lucidity cannot or does not exist without waking enlightenment; it is obvious that it does. Similarly, deep sleep lucidity does not require waking or dreaming lucidity. Instead we speak of a natural progression: what is learned in waking tends to be carried into the dream state and what is practiced in both tends to lay the foundation for the awakening of formless, clear awareness in deep sleep.
As such, there also appears to be an evolutionary progression of wakefulness within these three states. While enlightenment can be thought of as an ongoing synthesis within the developmental dialectic of any and all stages of waking development, it is also generally associated with transpersonal and trans-rational development, meaning that it follows after growth of the self through prepersonal and personal developmental stages. As we have noted in the chapter on lucid dreaming, enlightenment within the dream state, at least from the perspective of waking consciousness, is lucid dreaming, which is similar to the awakening of a separate sense of self in a typical four-year-old. Lucid dreaming, as an evolutionary advance within the arc of dream state evolution, corresponds roughly with the late prepersonal level of waking development. Of course, enlightenment from the perspective of the collective consciousness that is the evolving self of the dream state is something much greater than the mere advancement of waking identity to lucidity within a dream.
Lucid deep sleep, when viewed within the evolution of formless consciousness known best through deep sleep and causal meditation, is a mere first awakening within deep sleep, a movement from the urobic involution of gestation to early prepersonal birth into the exterior world. The entire arc of deep sleep state evolution lies ahead when you become lucid in deep sleep. What does that evolutionary progression look like from the perspective of life itself? What are the evolutionary stages of oneness? While the four types of mysticism, energic, subtle, causal, and integral, may represent a shadow of the evolution of the formless deep sleep state, and while we may look to the increasingly subtle levels of meditative consciousness described by various schools within Buddhism for echoes of this progression, it is important to remember that these are still projections by human consciousness and its perspective upon a developmental process (lucid deep sleep) that is not about the self, but about life, and which the self does not and cannot comprehend, because life is, by definition, far broader than any self or Self. As a dream yoga, Integral Deep Listening provides experiences of a non-self-centered, polycentric identity of the type indigenous to the evolution of dream consciousness, and the formless, focused clarity inherent within lucid deep sleep. These are both necessary prerequisites to getting out of your own way and “getting over yourself,” so that you may be able to more fully participate in life’s agenda for its own unfolding.
 Wilber, K. One Taste, Shambhala, Boston. pp, 75-76
 Qualities of the Four Rupa Jhanas: For each Jhāna are given a set of qualities which are present in that jhana:
- First Jhāna — the five hindrances have completely disappeared and intense unified bliss remains. Only the subtlest of mental movement remains, perceivable in its absence by those who have entered the second jhāna. The ability to form unwholesome intentions ceases. The remaining qualities are: “directed thought, evaluation, rapture, pleasure, unification of mind, contact, feeling, perception, intention, consciousness, desire, decision, persistence, mindfulness, equanimity & attention”
- Second Jhāna — all mental movement utterly ceases. There is only bliss. The ability to form wholesome intentions ceases as well. The remaining qualities are: “internal assurance, rapture, pleasure, unification of mind, contact, feeling, perception, intention, consciousness, desire, decision, persistence, mindfulness, equanimity, & attention”
- Third Jhāna — one-half of bliss (joy) disappears. The remaining qualities are: “equanimity-pleasure, unification of mind, contact, feeling, perception, intention, consciousness, desire, decision, persistence, mindfulness, equanimity & attention”
Fourth Jhāna — The other half of bliss (happiness) disappears, leading to a state with neither pleasure nor pain, which the Buddha said is actually a subtle form of happiness (more sublime than pīti and sukha). The breath is said to cease temporarily in this state. The remaining qualities are: “a feeling of equanimity, neither pleasure nor pain; an unconcern due to serenity of awareness; unification of mind, contact, feeling, perception, intention, consciousness, desire, decision, persistence, mindfulness, equanimity & attention”. The Arupa Jhānas: Beyond the four jhānas lie four attainments, referred to in the early texts as aruppas. These are also referred to in commentarial literature as immaterial/the formless jhānas (arūpajhānas), also translated as The Formless Dimensions, in distinction from the first four jhānas (rūpa jhānas). In the Buddhist canonical texts, the word “jhāna” is never explicitly used to denote them, but they are always mentioned in sequence after the first four jhānas. The immaterial attainments have more to do with expanding, while the Jhanas (1-4) focus on concentration. The enlightenment of complete dwelling in emptiness is reached when the eighth jhāna is transcended.
The four formless jhanas are:
- Dimension of Infinite Space – In this dimension the following qualities are “ferreted out”: “the perception of the dimension of the infinitude of space, singleness of mind, contact, feeling, perception, intention, consciousness, desire, decision, persistence, mindfulness, equanimity, & attention”.
- Dimension of Infinite Consciousness – In this dimension the following qualities are “ferreted out”: “the perception of the dimension of the infinitude of consciousness, unification of mind, contact, feeling, perception, intention, consciousness, desire, decision, persistence, mindfulness, equanimity, & attention”.
- Dimension of Nothingness – In this dimension the following qualities are “ferreted out”: “the perception of the dimension of nothingness, singleness of mind, contact, feeling, perception, intention, consciousness, desire, decision, persistence, mindfulness, equanimity, & attention”
Dimension of Neither Perception nor Non-Perception No qualities to be “ferreted out” are being mentioned for this dimension.
The Buddha also rediscovered an attainment beyond the dimension of neither perception nor non-perception, Nirodha-Samapatti, the “cessation of feelings and perceptions”. This is sometimes called the “ninth jhāna” in commentarial and scholarly literature.
(The above is taken from the Wikipedia article on Dhyana in Buddhism, following the Anuppada Sutta.)