Scientists at UCSF have uncovered a surprising culprit behind brain aging: a protein called FTL1. In mice, too much FTL1 caused memory loss, weaker brain connections, and sluggish cells. But when researchers blocked it, the animals regained youthful brain function and sharp memory. The discovery suggests that one protein could be the master switch for aging in the brain — and targeting it may one day allow us to actually reverse cognitive decline, not just slow it down.