The Mundaka Upanisad brings an interesting verse that explains how the different states of consciousness we experience are connected with the soul, and ultimately with the Supersoul inside the heart.
This is text 2.2.6:
arā iva ratha-nābhau saṁhatā yatra nāḍyaḥ
sa eṣo ’ntaś carate bahudhājāyamānaḥ
om ity evaṁ dhyāyatha ātmānaṁ
svasti vaḥ pārāya tamasaḥ parastāt
“All the nāḍis of the body are fixed to the heart, like spokes to the central hub of a chariot wheel. The Lord moves about within, manifesting in many ways. Meditate on this transcendental Lord through the transcendental sound vibration and by His mercy, cross beyond the darkness of ignorance. May you be blessed.”)
The nāḍis are subtle energetic pathways, through which the vital airs flow. There are thousands of nāḍis in the body, and they intersect in the chakras. Because they are very subtle pathways, the nāḍis are not understood in modern medicine (which is limited to the study of the nerves and the circulatory system), but nāḍis receive great importance in the Vedic sciences.
All the nāḍis are connected to the heart, and the reason they are connected to there, and not some other part of the body, is because the Lord is there, as Paramatma. Because the ātmā (the Lord) is inside the heart, togueter with the other ātmā (the spirit soul), the heart is the center of energy for the whole body. The Lord permeates the whole body, just like He permeates everything with His potency, and that’s how the body can function. Because the potencies of the Lord circulate through the whole body maintaining all the organs, etc. it is said that the Lord moves (antaś carate) inside the body.
The word bahudhā means “in various forms. The potency of the Lord manifests in the different states of consciousness: viśva (the awaken state), taijasa (the dream state) and prājña (deep sleep). In the viśva state, the consciousness of the soul is connected with the senses, and one becomes aware of the outside world, free to perform activities according to his desires. In the taijasa state, the consciousness is disconnected from the external senses, but still acts through the mind, in dreams, while in the prājña state, the consciousness fully retracts to inside the heart and merges into Paramamatma. The soul then rests from material activity. All these states of consciousness emanate from the Lord and are thus connected with Him.
By the transcendental vibration, the oṁkāra, or the mahā-mantra, we can focus our meditation on the transcendental Lord, and thus gradually recover our original consciousness, that has been for so long covered by false material identification. By doing so, one can attain the state of turīya, the fourth state of consciousness, where the soul reattains his original, transcendental consciousness.
These four states of consciousness are described in the Mandukya Upanisad, which is the shortest of the Upanisads. It was spoken by Varuna, who assumed the form of a frog (maṇḍuka).
Mayavadis gives a monistic interpretation of these verses, with the individual soul being the cause of the different states of consciousness and the ultimate stage as merging into Brahman. This is however not what the verses speak about. The Lord is the source of the different stages of consciousness experienced by the soul, and ultimately He is their supreme enjoyer. In fact, each of the four stages is a manifestation of the Lord. Turīya is thus simultaneously a state of consciousness and a form of the Lord, the same for Taijasa and so on, just like Vāsudeva is an expansion of the Lord, the source of consciousness and also a state of consciousness. The ultimate goal is to revive one’s original consciousness as an eternal servant of the Supreme Lord, beyond all material contamination.
Here are the verses with a translation from the Vaishnava perspective:
1- Om-ity-etad-akṣaram-idam sarvam, tasyopavyākhyānam bhūtaṁ bhavad bhaviṣyad iti sarvam-omkāra eva, yac ca anyat trikālātītam tad api omkāra eva.
Om. Indeed, this imperishable syllable is everything. All that is material exists under the purview of past, present, and future, and all of that is Om. And everything that transcends space and time (the spiritual realm) is also Om. There is nothing apart from the Lord.
2- sarvam hyetad brahma ayam-ātmā brahma so’yam-ātmā catushpat
All of this is indeed Brahman. This Supreme Self (the Supreme ātma) is Brahman and manifests in the body in four states of consciousness, experienced by the conditioned soul (the minute ātma).
3- jāgarita-sthāno bahiḥ-prajñaḥ saptāṅga ekonaviṁśatimukhaḥ sthūla-bhug vaiśvānaraḥ prathamaḥ pādaḥ
The first state is the waking state (viśva), where consciousness is directed outward, connected with the seven limbs and the nineteen faculties (the five sense organs, the five organs of action, the five vital airs, and the four internal senses; mind, intelligence, ego, and material consciousness). In this state, the soul becomes the enjoyer of the objects of the senses that are part of this world, called Vaisvanara, the universal form of the Lord.
4- svapna-sthāno’ntah-prajñaḥ saptāṅga ekonaviṁśatimukhaḥ praviviktabhuk taijaso dvitīyaḥ pādaḥ
The second is the dreaming state, where consciousness is turned inwards. In this state, called taijasa, the seven limbs and nineteen faculties contact subtle sense objects in dreams. In this way, the soul enjoys dreamy experiences, enabled by the Taijasa, the luminous Lord.
5- yatra supto na kancana kāmam kāmayate na kancana svapnam paśyati tat sushuptam, sushupta-sthāna ekībhūtaḥ prajñānaghana evānandamayo hyānandabhuk cetomukhaḥ prajñaḥ tritīyaḥ pādaḥ
The third is the state of deep sleep, called prājña, where one does not desire anything nor see any dreams. In this state, the soul experiences a blissful state of union with the Prajñānaghana (the Lord, the undivided source of consciousness) through the gateway of pure consciousnes.
6- eṣa sarveśvara eṣa sarvajña eṣo’ntaryāmī eṣa yoniḥ sarvasya prabhavāpyayau hi bhūtānām
This Supreme Self, the Lord of all, the Supreme Lord, is omniscient and all-knowing (sarvajñaḥ), the inner controller (antaryāmī), the source of everything. Indeed, He is the origin and dissolution of all beings.
7- nāntaḥ-prajñaṁ na bahiḥ-prajñaṁ nobhayataḥ-prajñaṁ na prajñāna-ghanam na prajñaṁ nāprajñaṁ adṛṣṭam-avyavahāryam-agrahyam-alakṣaṇam-acintyam-avyapadeśyam-ekātma-pratyaya-sāram prapañcopaśamam śāntam śivam advaitam caturtham manyante sa ātmā sa vijñeyaḥ
In the fourth state, the individual soul re-attains his original state of consciousness. This consciousness is not connected with a material body in any way. It is not turned to the outside, nor the inside, it is not materially conscious or unconscious. It is also not a state of unconscious contact with the Lord. This original state of consciousness is beyond the perception of the senses, beyond the comprehension of the mind, beyond the speculations of intelligence, and the perception of material consciousness. This ultimate state consists of the spiritual awareness of the soul, beyond the material manifestation. This state, beyond material duality and fully auspicious, is called turīya. It should be realized as the ultimate knowledge (vijñeyaḥ).
8- so’yam-ātmā adhyakṣaram omkāro’dhimātram pādā mātrā mātrāś ca pādāḥ akāraḥ ukāraḥ makāra iti
This Supreme Self, indeed, is the syllable Om, which encompasses all measures. The states of consciouses are represented in the constituent phonemes of the syllable, the letters A (akāraḥ) U (ukāraḥ), and M (makāraḥ).
9- jāgarita-sthāno vaiśvānaro’kāraḥ prathama mātrā apterādimatvād-vāpnoti ha vai sarvān kāmān ādiś ca bhavati ya evaṁ veda
The waking state, connected with Vaiśvānara, the universal form of the Lord, is associated with the letter A, the first part of the syllable Om, because is associated with the all-encompassing and primordial nature of the Lord. One who knows this attains all his desires and becomes foremost.
10- svapna-sthānas taijasa ukāro dvitīyā mātrā utkārṣād-ubhayatvād-utkṛṣyati ha vai jñāna-santatim samānaś ca bhavati na syābrahmavit kule bhavati ya evam veda
The dream state, taijasa, is associated with the letter U, the second part of the syllable Om, because of its excellence and its position in the middle, drawing the soul from outward state, into the interior world. One who knows this attains an unbroken flow of consciousness and becomes free from material contamination. None of his descendants will lack spiritual knowledge.
11- suṣupta-sthānaḥ prājño makāras tṛtīyā mātrā miter-apiter vā minoti ha vā idam sarvam-apitiś ca bhavati ya evaṁ veda
The state of deep sleep, prajña, is associated with the letter M, the third part of the syllable Om because it is connected with the all-encompassing and all-absorbing nature of the Lord as the creator and destroyer of everything, including all external consciousness. One who knows this fully understands this material manifestation.
12- amātras-caturtho’vyavahāryaḥ prapañcopaśamaḥ śivo’dvaitaḥ evam omkāra ātmaiva samviśaty-ātmānam ātmānāṁ ya evam veda
The fourth state, turīya, is beyond sound, beyond actions and interactions. It is the cessation of all material phenomena, beyond material duality and fully auspicious. This omkāra is indeed the Supreme Self. One who knows this attains the Supreme Self, entering into the spiritual nature.
