I’m often asked how the dying process works with things like dementia and the loss of cognitive function. This is where it helps to know about the triune, or three-part, nature of mind and body. In the broadest terms, these are the outer gross body that supports gross levels of consciousness; the inner subtle body that supports subtle consciousness; and the very subtle or indestructible body that supports a very subtle awareness. The outer body is where we can correctly assert that mind equals brain. This gross outer body and mind is what dissolves in the five stages of the outer dissolution, which itself goes from gross to subtle (from earth to water to fire to wind to space).
Dementia and the like affect this level of body and mind. But this is just the surface of our being, the part of us that is most affected by form (body). This is the level that is also affected by mind-altering drugs, like pain medications or other psychotropic agents. If this outer level is all we identify with, and for most of us it is, we’ll suffer in direct proportion to our level of identification when this outer level dissolves.
Spiritual practice is in large part about differentiating from (dying to, letting go of) this outer level, and coming to identify with deeper and therefore truer levels of our being: the subtle and then very subtle levels (the innermost level in Buddhism is actually called the “truth body,” or dharmakaya). When we die, we’re going to drop through the outer gross levels (and through the five stages of the outer dissolution), into the intermediate subtle levels (and through the three stages of the inner dissolution), to finally arrive at the moment of death (the moment of truth body) at the innermost very subtle level (stage nine of the death process). Death is the death of form, going from gross to very subtle, from the fully formed to the fully formless, from false levels of identification to the truth.
Spiritual practice is therefore a kind of death in slow motion, a transition from gross states of mind to extremely subtle states of mind. If we can cultivate these extremely subtle states of mind while we’re still alive, we won’t be affected when the gross levels decay or dissolve. In other words, dementia and the like have no affect on the deeper levels of mind. Indeed, the deepest level is called “the changeless nature,” which means that nothing on the outer surface of our being can affect this deepest level. The outer level is like the surface chop on the ocean, which has absolutely no affect on the bottom of the ocean. Drop to the bottom of your mind now, and you can “look up” at all the surface chop without being affected by it. Dropping to the bottom is what we are forced to do when we die, and what we are invited to do on the spiritual path.
So for someone still fully identified with surface structures, situations like old age, sickness (dementia), and death are a big deal. Everything you know is being lost. But for someone who has already let go of these surface structures, and takes ultimate refuge in more formless (and therefore deathless) aspects of their being, things like old age, sickness, and death are no big deal.
In terms of memory, spiritual practices, while starting with the surface mind, “stamps” the intermediate subtle body and mind. It’s a form of “downward causation.” While you cannot change the very subtle body and mind (“the changeless nature” that doesn’t require any change, it’s always already awake and complete), you can change the intermediate subtle body and mind. Spiritual practice does this in general, and processes like the inner yogas (that work with “nadiplasticity”), does it in particular. You can download propensities and subtle memories into this intermediate level, memories and propensities that can serve you when you descend into this level in the intermediate stages of death.
Someone with a well-trained mind can still have their outer levels of mind/body be afflicted by dementia and cognitive decline, but they have already differentiated from (died to, let go of) these levels and take deeper refuge “below.” When these deeper levels are “stocked” with subtle memories of spiritual practice and study, that stockpile of wisdom (and compassion) can come to the rescue as everything on the surface of life falls apart.
This is the whole point of bardo yoga, and deep spiritual practice: to stockpile wisdom and compassion (the “two accumulations” in Buddhism), and to die before you die (to transcend, or “subscend,” the ego, which is nothing more than exclusive identification with form). So remember, “If you die before you die, then when you die you will not die.” When you come to fully release all the outer levels, and fully identify with the innermost level, that level is deathless because it’s formless. Identify with the truth, not with what obscures it. Then it doesn’t matter one bit what happens “up there.” This is why a realized being like His Holiness the 16th Karmapa could say just before he died: “Nothing happens.”