Researchers learn how to grow old brain cells

A new technique allows scientists to study diseases like Alzheimer’s and Parkinson’s using cells from human patients. Historically, animal models — from fruit flies to mice — have been the go-to technique to study the biological consequences of aging, especially in tissues that can’t be easily sampled from living humans, like the brain. Over the past few years, researchers have increasingly turned to stem cells to study various diseases in humans.