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Oh, the proverbial fountain of youth. As we age, can we somehow tap into it? Researchers are exploring this in a literal way as they study the effects of blood from human umbilical cords—which is about as young as it gets—on aging mice.

Reporting in the journal Nature, they found that mice injected with human plasma from umbilical cords (several times over the course of weeks) in late middle age seemed to acquire better memories.

The mice preformed better in maze tests, and memory-making genes in the brain fired back up. It's one of the first findings that young blood "might be having an effect on the brain itself," one researcher tells NPR.

Still, while an outside researcher tells Science magazine that these "are exciting results," others note that there are several caveats that temper them. First, they have yet to be replicated in humans.

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And the protein that seems to be helpful, TIMP2, happens to be found in higher levels in people with Alzheimer's. One leery researcher tells NPR that aging isn't about running out of positive things but about accumulating negative things.

Introducing new blood may only go so far in counteracting that accumulation, though more research may provide answers. (Some argue umbilical cords shouldn't be cut so fast.)

This article originally appeared on Newser: Blood in Umbilical Cord May Improve Our Memories