It's tempting to imagine the brain as a biological computer, with the tissue as hardware and electrical activity as software. If that were the case, mind transference might be technically feasible (albeit ethically fraught), at least pending the development of some extremely advanced electrode arrays. Extricating mind from matter, though, can't be done. "The self is in the structure," says Charles Higgins, a University of Arizona neuroscientist and electrical engineer. "It's in the interconnection of 100 billion neurons, and in the individual shape of neurotransmitters and receptors." Even if surgeons could successfully transplant a brain, they would have to transfer the spinal cord as well, or risk stripping the subject of a lifetime of muscle memory.

One workaround, says Higgins, could involve cloning. A clone with a structurally identical central nervous system could perhaps be stimulated with electrical signals that mimic the original.