A ‘cryosleep pod’ in the 1979 science-fiction film Alien.Credit: 20TH CENTURY FOX via AJ Pics/AlamyA familiar trope in science fiction is the cryopreserved time traveller, their body deep-frozen in suspended animation, then thawed and reawakened in another decade or century with all of their mental and physical capabilities intact.Researchers attempting the cryogenic freezing and thawing of brain tissue from humans and other animals — mostly young vertebrates — have already shown that neuronal t...