(From DukeMedNews). Scientists appear to have reconciled the observed lower rate of neurogenesis in the aging brain with the fact that stem cells are still present: "as the brain ages, fewer new nerve cells, or neurons, are born in the hippocampus, the brain's learning and memory center. ... The common assumption had been that the brain drain was due to a decreasing supply of neural stem cells in the aging hippocampus ... in young rats, the hippocampus contained 50,000 stem cells - and, significantly, this number did not diminish with aging. This finding, the researchers said, suggested that the decreased production of new neurons in the aged brain was not due to a lack of starting material. ... The team now is searching for ways to stimulate the brain to replace its own cells in order to improve learning and memory function in the elderly." This sounds much like the debate over the declining ability of stem cells to repair aging muscle - stem cells are present, but they do less work.