Aquarius said:
Let's say a person becomes severely demented, or has elzheimers, then dies, do they get conscious again after dying?
I can tell you the experience I had with my mother's case, although she didn't have dementia or Alzheimer's disease. She had cancer and the cancer had moved in her brain and had made her paranoid, or very veeery weird, forgetful etc... This whole thing lasted for less than a month though. In her last days her body was completely immobilized, eyes closed, she could neither talk nor move. We don't know if she could hear us either.
After her death, my sister saw her in her dreams. She saw her looking young and being very happy.
I had seen her too at some point.
Anyway, a few months later I had to do a surgery, and I was then lying at my bed, being in a lot of pain. I thought of my mother, and how I missed her comfort when I was sick, and I felt her very intensely as if she was (and I believe she was) in my room, giving me comfort with her presence.
So, the cancer, or the issues it created to her brain and body didn't follow her in the afterlife.
Of course these effects hadn't lasted long while she was alive (less than a month), but she had had cancer for... it must have been 20 years in total; and was forced to butcher her body, one body part at a time. Thank jews for all of this. May they all be cursed and rot physically and spiritually.
Anyway, I think NakedPluto's response was right on point; but maybe my own experience may help you out as well.