A. Our Naked Consciousness
In devachan, after the death of the kāmarūpa and after the gestation period, our 'naked' consciousness, deprived of physical as well as coarse astral matter, liberated from kāma and the mind which was involved and interested in mundane matters, shines forth in full bloom and intensity. We experience the realization of the highest ideals and occupations our minds had during physical incarnation. No near-death experiencer or spiritualist has any means to form an idea of the experience called devachan, or 'heaven'. Because of the absence of bodies and our lower psychologies we experience no suffering - only bliss - for hundreds or thousands of years it is said, but not eternally in the common sense of the word in a sphere where time does not exist, nor any properties of matter (like the three dimensions) to impede our blissful consciousness. This consciousness is said to be of far greater intensity and spirituality than anything even an average mystic experiences on Earth.
But it is temporary. When all the lofty imaginations of our mind have found their sway, we descend step by step to a next incarnation on Earth, to work and slave in the half-conscious gloom that we know so well from our normal daily experience. We will have a vision again before being born, in which we understand the purpose and karmic reason for our coming earthly life. There may be an element of choice in it, depending on our wisdom and courage. Then again the consciousness faints for the individual that we are, to reawaken step by step before and after our next birth from a woman's womb.
Consciousness is eternal, and though sometimes experienced as intense and at other times fainted beyond our personal grasp, it is continuous as life itself, and not at all a product of physical matter. Matter, either physical or astral or subtle, is temporarily attracted towards and a nucleus of consciousness which in Theosophy is called the 'Reincarnating Ego'
B. What is Existence?
The karmic record which contains all that is thought and done during life on earth and the subtle prāṇas always remain with the reincarnating Ego between death and rebirth. It seems not logically impossible that the imperceptible record consists of structures which are as complex as, or are more refined and complex than the physical brain. However because the realms of subtle matter have their own laws of which we know little, it may be that 'complexity' is not the right term. Because all structures of all bodies are retraceable to the activity of the Self, one might assume that the non-physical records have at least the same or an even greater complexity - these bodies must at least carry the causal seeds of such complexity in physical matter. Or is contains the vibratory principles in ākāśa (aether) which work in or interfere in such a way on the 'crystallized vibrations' known on the astral (liṅga) matter particles to which physical bodies as we know them are going to be precipitated. In modern technology and science we know that codes based on a simple equation (0 and 1) can become visible on computer or TV screens; or on four or five chemical bases in DNA and RNA, which define for the synthesis of complex structures of physical matter which we call bodies and material things. The code on a hard disk or a DNA strand is able to produce the illusions we know as films or physical bodies. Physical matter consists basically of attenuated bunches of whirling energy with very much larger 'empty' spaces in between. This might be the technology of nature to manifest bodies on a specific level of possible perception. Is perception an interpretation of holograms purposely chosen by our inner conscious being? Is the universe an instantaneous hologram in which time and space themselves are illusions created for a purpose by our inner consciousness? Would this imply that we may phrase concepts like zero-time eternity and zero-measure space? Is and was and will be every thing that existed, exists and will exist always there? Is it our deepest inner spiritual Mind which is itself a reflection of Consciousness - that what is eternal and infinite but yet timeless and spaceless? Is all existence, from the viewpoint of an individual being, an illusionary image created through a different point of a space and timeless 'hologram' as space-and-time reality? Then we seem to approach very close to the Buddhist Mind-Only School (Yog(Yogāc(h)āra or C(h)ittamātra) as expressed in the Laṅkāvatāra Sūtra?[1] This sūtra states that everything that exists is a product of the mind only, and that nothing in the universe has any existence on its own behalf, and that apparent processes like birth and death, evolution and causality are created by the mind only. This is also confirmed by the great Indian advaitin (= non-dualist) Śaṅkarācārya. Nevertheless, it seems to me, Nature herself must have a 'reason' to create these illusions. It is generally called māyā (very deludingly translated as 'illusion') - that which apparently, but not really - can be measured (Skt. mā = to measure, to create). In reality māyā is everything that can be created by Mind - cosmic Mind or individual mind i.e. all that can be 'measured' because it has a beginning and end, all that can be perceived and experienced. Māyā is the mother of duality and the cause of all problems. But māyā is not separate from Reality.
However, the fact that everything we and all other centers of consciousness, are nothing but points of view, does not make māyā less essential or interesting or even useless. Māyā contains all that is joy and where we go for. Māyā is the one instrument in the universe that makes conscious beings go from nonself-consciousness to consciousness. It is existence itself. One day we will understand what existence really is.
In any case, from our relative point of view, we ourselves being parts of existence or māyā, consciousness and life continue after death. Experiences, conscious states of existence, described as to exist in many different non-physical environments are the experienced states of consciousness which result from the activity of the mind when embodied in a physical brain in the most recent life. These experiences including 'hells' (nāraka) and 'heavens' (devaloka), kāmaloka and devachan etc. are states of consciousness experience as well as states of embodiment in subtle, i.e. one or other phase of astral matter.
So the answer to the question whether consciousness is a function of the physical brain is: No.
In the previous articles it has been shown sufficiently plausible that consciousness can and does exist independent of a physical brain; consciousness can exist within physical beings without a brain. Consciousness existed before the physical brain, as well as after its destruction. The Self or ātma or jīva, though not having a brain, is all-containing.
Also, consciousness can exist without any (organic) brain or nervous system at all, as in minerals. Modern biology knows that microorganisms are able to perceive and process information without brains, but that conscious processes have a relation with the cytoskeleton and the cell membrane. Moving cells perceive light as well as chemical and tactile information and react in individual ways. Cytologist Albrecht-Buehler (2013) in his web-article Cell Intelligence[2] describes in detail how two perpendicular microtubuli in the centrosome of a moving cell have light-sensitive spots which give the cell the possibility to three-dimensionally determine the direction of incoming light. The information thus acquired is transported electrically along the cytoskeleton related 'nervous' system in the cytoplasm of cells and the transfer of this information to induce particular parts of the cytoplasm to form pseudopodia that make the cell move in a chosen direction. Perception, and sending out electrical energy into different reactions to influence cytoplasm is focused in the centrosome outside the cell's nucleus, and the processes maintain no direct relationship with the genetic code inside the nucleus.
Physical consciousness only makes sense when there is a physical body. If physical consciousness appears to exists outside the physical body (e.g. after death, as found by spiritualists) it must be 'astral memory,' - memory that is recorded in subtle matter - because the sense organs to receive new input of the plane of physical information are absent. Also the subtle body has sense perception on its own level, but subtle matter is not hindered by physical obstructions. Emotional, psychological, intellectual and mental consciousness are not confined to the physical body, because as Theosophy describes in detail and logically that these forms of consciousness also exist after death in absence of the physical brain.