Gut bacteria may steer aging memory through the brain–gut nerve highway

In mice, age-related memory decline appears driven by the gut microbiome, especially Parabacteroides goldsteinii, which raises gut metabolites (MCFAs like 3-HOA) that promote inflammation and weaken vagus-nerve signals to the hippocampus, impairing memory formation; boosting vagal activity or blocking MCFA effects reversed the decline, suggesting interoception-based approaches could slow cognitive aging in humans, though confirmation in people is needed.