A large international brain study has revealed that memory decline with age is not caused by a single brain region or gene. These are extensive structural changes in the brain that accumulate over time. The researchers analyzed thousands of MRI scans and memory tests from healthy adults. They found that memory loss accelerates as brain tissue shrinks, especially later in life. The hippocampus plays a key role, but many other areas of the brain also contribute. These areas create widespread vulnerability instead of isolated damage.