The later is surely science fiction, but brain transplants - which really, are just figuring out how to perfectly reconnect spinal tissue, which while incredibly hard is not something completely fictional since we have <i>already done it</i> in very reduced test cases (and we know that stem cells are likely going go give us an easy way eventually to just regrow the gaps in the spinal column) are not nearly as far out as nanites <i>of the sophistication to modify organic cells</i> are right now.