Rejuvenating weary old minds with injections of youthful blood sounds like a pseudoscientific "elixir of youth" dreamed up by a vampire. But nevertheless, there’s some evidence to suggest this bizarre-sounding technique could help recharge the brains of old mice. In a new study, scientists have begun to figure out how.

New research from the University of California, San Francisco, has been testing out this technique on mice by linking the vascular systems of an older mouse and a younger mouse. Their findings, recently published online in the journal Cell Reports, suggest that the procedure increases levels of Tet2, an enzyme that could be associated with brain-boosting benefits in mice.

After the infusions, the older individuals were found to have boosted levels of Tet2 in the hippocampus, the part of the brain associated with learning and memory. Tet2 is an enzyme known as an epigenetic regulator, responsible for the control of gene expression to promote brain regeneration. It’s believed that the loss of this enzyme could be partly responsible for age-related cognitive decline. All of this, the researchers say, hints that blood infusions could help ward off cognitive decline and memory loss as we age.

"At first I didn't believe it," lead author Geraldine Gontier explained in a statement, "I did the experiment again and again to make sure that it was right. But it became clear that some circulating factor in the blood is able to change the level of Tet2 in the brain."

In another part of the study, the scientists blocked Tet2 activity in the hippocampi of young adult mice and made them run a maze to test their learning and memory skills. As they expected, these mice were notably worse at performing the task. It was also found to significantly reduce the birth of new neurons. They then used custom-designed viruses to cause over-expression of Tet2 in the brains of mature mice. Lo and behold, this improved their memory.

“This was amazing because it’s like improving memory in a healthy, 30-year-old human,” said Saul Villeda, an assistant professor of anatomy.

“This finding is exciting on many levels,” Gontier added. “I’ve spent my entire PhD and now my postdoc trying to understand how the brain ages and how can we reverse it. And in this study, we find that one molecule, Tet2, is able to rescue regenerative decline and enhance some cognitive functions in the adult mouse brain.”

It isn’t clear exactly how Tet2 levels drive improved learning and memory in the mouse brain, let alone whether it will have a similar effect on humans, so don't get any ideas just yet. However, in theory, this discovery could lead to new therapies for maintaining healthy brain function into old age.