to the one who said s/he sees dead people, my advice is that you read neurology about hallucinations. in short you don’t SEE dead people, you THINK that you see them. what brain does is the subject of neurology. google CAUSES OF HALLUCINATIONS.
I suggest you find out what exactkt the word ‘ghost’ means and then think your question over, especially that you are asking THAT on an ATHEISTS’ site. ‘Ghosts’ don’t exist. Nothing supernatural exists.