Continuing the discussion from 
Project Skyscraper - Timeline / Storyline Thread:
Ghost being inside the core was my theory as well. Ghost=spirit or soul. The Core if you will. just from what I have read from WT narrative, and looking at what we see here, I believe the question of Who are you if you don’t remember anything is being developed. To anthropomorphically analyze it if you develop dementia and can’t remember anything, the part that makes you still you is Ghost, here he just gets to talk to the doctor(architect) about the things/ways that help dementia patients remember(think the piano from The notebook)