Why do our brains age?

One of the key factors that makes the brain age has been uncovered by scientists in the US. Young mice infused with the blood of older animals developed a drop in their cognitive abilities. This is down to a chemical made by the immune system called beta2-microglobulin. Why it has this pro-ageing effect, we don't know; but, encouragingly, removing it reverses cognitive decline, and promotes the growth of stem cells throughout the body and brain. Chris Smith spoke to Saul Villeda and the University of California, San Francisco to find out more.... Like this podcast? Please help us by supporting the Naked Scientists