Chemicals given to rhesus macaques blocked a brain molecule that slows the firing of the brain's nerve cells, or neurons, as we age—prompting those nerve cells to act young again.

"It's our first glimpse of what's going on physiologically that's causing age-related cognitive decline," said study leader Amy Arnsten, a neurobiologist at Yale University.

"We all assumed, given there's a lot of architectural changes in aged brains ... that we were stuck with it," Arnsten said.

But with the new results, "the hopeful thing is that the neurochemical environment still makes a big difference, and we might be able to remediate some of these things."

As the brain gets older, the prefrontal cortex begins to decline quickly.

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