Some brains seem to defy Alzheimer’s. Even when the disease’s telltale plaques and tangles are present, certain individuals remain mentally sharp well into old age. This phenomenon, known as cognitive resilience, is one of the most intriguing puzzles in neuroscience today.

At the Netherlands Institute for Neuroscience, researchers led by neuroscientist Evgenia Salta have uncovered new clues. Their work suggests that resilience may depend not on the sheer number of brain cells, but on how a special class of cells, called immature neurons, respond to damage.

For decades, neuroscientists have debated whether the adult human brain retains any meaningful population of “immature” neurons, youthful-looking cells tucked inside the hippocampus.