While it seems logical that age-related cognitive decline would be blamed on brain aging and degeneration (which, like anything in the brain, is notoriously hard to treat), there’s some evidence that processes elsewhere in the body influence the brain’s ability to form memories. In particular, neuronal pathways that sense the status of other organs in the body can influence cognitive functions in the brain.

Other studies have shown that our gut microbiome affects learning, memory, and behavior. But what we don’t yet understand is how these connections work—the specific molecules, microbes, and gut-brain communication involved—and whether we can use that knowledge to prevent or reverse age-related memory loss.

In our new work published today in Nature, we discovered that the aging gastrointestinal tract produces specific molecules that blunt the activity of a key gut-brain neuronal pathway, leading to age-related cognitive decline in mice.