Memory loss is fuelled by gut microbes in ageing mice

Memory loss is fuelled by gut microbes in ageing mice Skip to main content Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript. Advertisement Email Bluesky Facebook LinkedIn Reddit Whatsapp X Some bacteria in the intestines of mice increase in abundance as the animals age. Credit: Prof Cinti & V. Gremet/Science Photo Library A species of gut bacteria that proliferates as mice get older plays a part in the animals’ cognitive decline, a study finds 1 . Researchers determined that the bacterium interferes with signalling along sensory nerves connecting the gut to the brain. Although the experiments were conducted in mice, the gut–brain circuit that the team identified “is likely conserved in humans”, says David Vauzour, a biochemist at the University of East Anglia in Norwich, UK. That would need to be confirmed, but if the circuit is present in humans, then this research could reveal a mechanism that explains why people’s memory and ability to learn naturally decreases with age — and offer hope that gut-targeted therapies could reverse the decline. The effects of the bacteria, which dampens the gut–brain circuit in mice, seem similar to other consequences of ageing. “When we get older, we need things like glasses and hearing aids”, says co-author Christoph Thaiss, an immunologist at Stanford University in California. The study — published today in Nature 1 — shows that, just as ageing causes a decline in sensory perception of the external world, it might also be causing a loss of perception of internal signals, too, he says. Memory testing To explore how gut microorganisms contribute to ageing , the researchers housed ‘young’ mice that were two months old with ‘old’ mice that were 18 months old. That’s like having a person in their late teens live in close quarters with a person in their late 50s. How fast your brain ages is affected by these 64 genes After a month of living in the same cage, the young mice began performing in a similar way to the old mice on a maze task and another memory test. In the latter test, mice usually remember objects that they’ve seen before and therefore spend more time exploring new objects. But the younger animals that had been housed with the old ones instead spent equal time investigating both familiar and new objects — just as their older counterparts did. This indicated that they had lost their short-term memory. “Their deficit was so profound, they were basically undistinguishable from the old mice,” says co-author Timothy Cox, a neuroscientist at the University of Pennsylvania in Philadelphia. “It was almost unbelievable.” What had changed was that the young animals’ microbiomes had become similar to those of the older mice. By living near and eating each other’s faeces, mice can easily transmit their gut microbes to one another. The researchers suspected that one or more species of bacteria found in the gut of the old mice might be causing cognitive decline. Therefore, they colonized young mice with various bacterial species and zeroed in on one in particular, Parabacteroides goldsteinii . When the team transplanted this bacterium into young mice, it worsened their ability to remember objects that they had seen before. In addition, giving old mice antibiotics that wiped out their gut bacteria or a phage therapy that killed P. goldsteinii improved the animals’ performance on the same task — to levels comparable with young, healthy mice. Enjoying our latest content? Log in or create an account to continue Access the most recent journalism from Nature's award-winning team Explore the latest features & opinion covering groundbreaking research Access through your institution or Sign in or create an account Continue with Google Continue with ORCiD doi: https://doi.org/10.1038/d41586-026-00768-6 Read the related News & Views ‘ Gut microbes affect cognition during ageing ’ References Cox, T. O. et al. Nature https://doi.org/10.1038/s41586-026-10191-6 (2026). Article Google Scholar Download references Reprints and permissions Related Articles What accelerates brain ageing? 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