Centuries ago, Yajnavalkya used the analogy of “the great fish which travels along both banks, the nearer and the farther” while referring to the human consciousness which oscillates between the waking and the deep sleep state (Brihadaranyaka Upanishad 4.3.17). He wrote that when the Atman “rests in the intermediate state (of dream)”, it sees both states – waking and deep sleep (Brihad. Up. 4.3.9). In the state of dreamless sleep, the Advaita Vedantins saw evidence of the existence of Brahman; they reasoned that if a person feels refreshed after sleep, it must be because the Atman had temporarily united with Brahman .
There are hopeful signs that the lumbering caravan of modern science, with its constellation of professors (tenured and untenured) commanding a phalanx of caffeinated, unwashed and overworked graduate students, all plodding methodically through the unmapped terrain of human consciousness with their peer-reviewed and statistically significant scientific experiments, might someday serendipitously confirm Yajnavalkya’s insight that it is the same Atman that persists across the three states of waking, dream and deep sleep. In order to demonstrate continuity, one would have to show that some kind of learning or a unique memory persists between these states.
In the 1950s, after brain waves were first discovered, Simon and Emmons reported an experiment in which they played a tape of answers to questions in a room of sleeping volunteers. After waking up, the volunteers could not recall anything, indicating that learning in sleep was not possible. The volunteers could recall nothing because when most people fall asleep, they enter the subconscious. It would take considerable yogic development to become conscious of the outer physical world during sleep. Recent experiments which test an elementary form of learning known as “Pavlovian conditioning” might provide a flicker of hope though.
A while ago, sleeping newborn babies were subjected to what is known as the Pavlovian conditioning test. William Fifer and his colleagues subjected sleeping newborn babies to a musical tone followed by a puff of air directed at the eyes. After repeated trials, the sleeping babies began to scrunch their eyes immediately after hearing the musical tone, indicating that they were anticipating the forthcoming puff of air. In another study, Sullivan subjected one-day old babies who were awake to a citrus odour and lightly stroked their head to produce a head-turn. The following day, the babies would instinctively turn their head after smelling the citrus odour. This response was observed irrespective of whether the babies were awake or asleep.
A recently-published study (August 26, 2012) conducted by scientists at Weizmann Institute in Israel now demonstrates that adults are also capable of the same type of sleep learning. Sobel and colleagues “repeatedly exposed the sleeping participants to pleasant odours, such as deodorant and shampoo, and unpleasant odours such as rotting fish and meat, and played a specific sound to accompany each scent”. It was found that “sleep conditioning persists even after they wake up, causing them to sniff strongly or weakly on hearing the relevant tone — even if there was no odour. The participants were completely unaware that they had learned the relationship between smells and sounds” in their sleep. The “sniffing responses were slightly more pronounced in those participants who learned the association during the rapid eye movement (REM) stage, which typically occurs during the second half of a night’s sleep”. This may be the first incontrovertible demonstration of sleep learning in human adult brains.
One has to wait to see if Sobel’s results can be replicated by other scientists, as is standard scientific practice, but for the purposes of a topical (and presumptuous) blog post, we can assume that will happen over time. A successful replication of Pavlovian learning may still not validate the Upanishadic assertions. Since science currently assumes that consciousness arises as an epiphenomenon of brain activity, Pavlovian learning during sleep can be easily attributed to the nugatory brain activity that persists during sleep. One has to come up with a test which is more compelling to prove that is the same Atman which persists across three states. Such a test might also require more spiritually evolved human beings who can meet the test criteria !
For the time being, “sleep learning” is an exciting field of science which needs to be monitored for further developments. I had appended this topic to the end of a previous article “Mental awareness in coma patients” but it deserves to be discussed independently so I fleshed it out separately here.
We turn now to some remarks that Sri Aurobindo made on the subject of dreams. While discussing the experience of “Samadhi” in The Synthesis of Yoga, he wrote:
It is quite possible indeed to be aware in the dream-trance of the outer physical world through the subtle senses which belong to the subtle body; one may be aware of them just so far as one chooses and on a much wider scale than in the waking condition: for the subtle senses have a far more powerful range than the gross physical organs, a range which may be made practically unlimited. But this awareness of the physical world through the subtle senses is something quite different from our normal awareness of it through the physical organs; the latter is incompatible with the settled state of trance, for the pressure of the physical senses breaks the Samadhi and calls back the mind to live in their normal field where alone they have power. But the subtle senses have power both upon their own planes and upon the physical world, though this is to them more remote than their own world of being 
And in this passage from The Letters on Yoga, he elucidates on the manner in which the human consciousness navigates the recondite “dream worlds”:
Ordinarily when one sleeps a complex phenomenon happens. The waking consciousness is no longer there, for all has been withdrawn within into the inner realms of which we are not aware when we are awake, though they exist; for then all that is put behind a veil by the waking mind and nothing remains except the surface self and the outward world – much as the veil of the sunlight hides from us the vast worlds of the stars that are behind it. Sleep is a going inward in which the surface self and the outside world are put away from our sense and vision. But in ordinary sleep we do not become aware of the worlds within; the being seems submerged in a deep subconscience. On the surface of this subconscience floats an obscure layer in which dreams take place, as it seems to us, but, more correctly it may be said, are recorded. When we go very deeply asleep, we have what appears to us as a dreamless slumber; but, in fact, dreams are going on, but they are either too deep down to reach the recording surface or are forgotten, all recollection of their having existed even is wiped out in the transition to the waking consciousness. Ordinary dreams are for the most part or seem to be incoherent, because they are either woven by the subconscient out of deep-lying impressions left in it by our past inner and outer life, woven in a fantastic way which does not easily yield any clue of meaning to the waking mind’s remembrance, or are fragmentary records, mostly distorted, of experiences which are going on behind the veil of sleep – very largely indeed these two elements get mixed up together. For, in fact, a large part of our consciousness in sleep does not get sunk into this subconscious state; it passes beyond the veil into other planes of being which are connected with our own inner planes, planes of supraphysical existence, worlds of a larger life, mind or psyche which are there behind and whose influences come to us without our knowledge. Occasionally we get a dream from these planes, something more than a dream, – a dream experience which is a record direct or symbolic of what happens to us or around us there. As the inner consciousness grows by sadhana(yoga), these dream experiences increase in number, clearness, coherence, accuracy and after some growth of experience and consciousness, we can, if we observe, come to understand them and their significance to our inner life. Even we can by training become so conscious as to follow our own passage, usually veiled to our awareness and memory, through many realms and the process of the return to the waking state. At a certain pitch of this inner wakefulness this kind of sleep, a sleep of experiences, can replace the ordinary subconscious slumber .
As when one walks in sleep through luminous dreams
And, conscious, knows the truth their figures mean,
There where reality was its own dream,
He knew things by their soul and not their shape
(Savitri, Book 2, Canto 14)
- Roebuck, Valerie J. (ed). The Upaniṣads. London ; New York : Penguin Books, 2003, 63-65.
- Sharma, Arvind. Sleep as a state of consciousness in Advaita Vedānta, Albany : State University of New York Press, 2004.
- Simon, Charles and Emmons, William. EEG, Consciousness and Sleep Science 30 November 1956: vol. 124 no. 3231 pp. 1066-1069; cited in Makin, Simon. “Sleep on it”, Scientific American blog, Nov 20, 2012.
- Fifer, William P., et al (2010). “Newborn infants learn during sleep”. Proceedings of the National Academy of Sciences, 107(22):10320-10323; DOI: 10.1073/pnas.1005061107
- Sullivan, R. M., Taborsky-Barba, S., Mendoza, R., Itano, A., Leon, M., Cotman, C. W., et al. (1991). “Olfactory classical conditioning in neonates”. Pediatrics, 87, 511–518.
- Weizmann Institute of Science. “Sleep learning is possible: Associations formed when asleep remained intact when awake.” ScienceDaily, 26 Aug. 2012. Web. 27 Aug. 2012.
- Costandi, Mo. “How to learn in your sleep”. Nature News, 26 August 2012.
- While you were sleeping. 26 August 2012. Science blogs.
- Sri Aurobindo. Synthesis of Yoga, CWSA vol 23-24, p 522
- Sri Aurobindo. Letters on Yoga, SABCL vol. 23, p 1024
- Towards more conscious sleep and dreams
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- Explaining out-of-body and near-death experiences
- Mental awareness in comatose patients and sleeping newborn infants
- Sleep and Dreams
- Birthmarks due to reincarnation
- Cases of reincarnation between Hindus and Muslims
- A contemplation exercise before going to sleep
- The Vijnana Bhairava Tantra
- The phenomenon of double consciousness
- The Milinda-Panha
- Vidyas in the Upanishads
- Vidyas in the Upanishads – part 2
- Links between Vedas, Upanishads, Tantra and Puranas
- Meditation techniques from the Yoga Upanishads
- Introduction to the Upanishads
- Memory transference in organ transplant recipients
- Progress reports of Sri Aurobindo
- Reconciling Samkhya, Vedanta and Tantra
- Difference between genius and mysticism
- Four epistemic methods of consciousness