Graham Hancock wrote a book about contacting the dead on psychedelics after his father died. It's called "Supernatural". He talks about taking DMT.
Yeah this book is totally worth reading and makes you think. Personally, I think the possibility exists until we can prove otherwise. I'd much rather keep my mind open to possibility than closed until there is a real way to determine a yes-no answer.
One thing that comes to mind is, if we are individual manifestations all of the same consciousness, if we are all like mushrooms arising out of the one same mycelium like signularity, and if the universe truly is like a hologram, then if I am alive and have an image or version of you in my seemingly individual mind while alive, and your individual body is killed, that version in my mind remains in the realm of the living, albeit not quite as it did when inside of its own fleshy container, but still it remains a part of the living world. What better meeting point for the denizens of the material end of the spectrum and the ethereal end than the vistas of the mind?
It reminds me a bit of the scene from the end of Contact when she meets up with a version of her father, which the alien life form used through her mind's memories as a familiar form to establish contact with her human mind.
Basically there's 2 main points to this: 1) once we're dead, what may remain will no longer be the dense, physical or material end of the vibratory spectrum of matter/energy, and 2) most religions have always sort of pushed the idea of a singular unity that is god that all are apart of, even if it leaves out the comforting language and merely describes it as the shimmering void of eternal consciousness or whatnot.
So take those 2 points, and think how a nonphysical being might be able to interact with a physical one...well, perhaps if there were some halfway point between the physical and nonphysical that could serve as a meeting point? And that is where I think the versions of the living that we build and construct in our minds come into play. It allows us, whether via external reception of information being communicated into that image or construct of the formerly living we hold inside of our minds, or even if it is a purely imaginary experience, role playing if you will, to connect with a version of the dead.
I'm not saying I believe in it either way, but i surely don't know enough to rule it out. I personally don't see any benefit in deciding either way so I just keep my mind open to any possibilities so that I don't tune out any experiences that I might have otherwise experienced.