what do you think happens to human consciousness after death ?
Consciousness is pre-death, by definition. Any experience experienced is a consequence of a dying brain. And any experience experienced requires a not-entirely-kaput brain, i.e., still pre-braindead-death.
Just about everyone dies from the same mechanism- the lack of blood/oxygen to the brain. We know the results of this. It just so happens the most sensitive parts of the brain to hypoxia and ischemia are the components of the limbic system like the hippocampus, which is involved in memory and emotion, and even time perception.
Long story less long, a dying brain suffers a neurochemical cascade, essentially a seizure in the memory part of the brain. Just as a seizure in the motor cortex results in outwardly apparent spasms, a seizure in the memory part of the brain results in a jumble of components of a lifetime of memory.
While the literature is laced with hokey new age rubbish about the afterlife, astral planes, other realms of consciousness, heaven, etc, the experience is real and the shortcoming is with the vocabulary and intelligence of those individuals who have been near-death attempting to explain the experience.
Long story short, there is nothing after death. But there is a perceived afterlife pre-death. Your lifetime of memories come together and your brain tries to weave a story with its components, and it feels eternal because the time perception parts of the brain are also going kaput. Not unlike dreaming, where bits from your memory get thrown together for a story, dream time doesn't correlate to real world time, and you don't know it was just a dream until you wake up. You don't wake up from the pre-death dream, you'll never know it's just a hallucination, it's as real as anything,
to you. And then there is no more you. (other than symbolically in the minds of others).