Brain cells in mice were shown to be capable of surviving at least twice as long as the mice they were once in, according to a study in the journal Proceedings of the National Academy of Sciences. The findings are said to have implications for "life extension enthusiasts" -- if "your neurons do not have a fixed lifetime," then perhaps humans can continue to extend their lifespan, says study co-author Lorenzo Magrassi -- as well as for those looking into neuronal transplants that could help with Alzheimer's or Parkinson's disease.