Many people’s brains deteriorate as they age, becoming riddled with malfunctioning proteins that result in cell death and the loss of memory and cognition. But other people’s brains remain almost perfectly intact, their thinking as sharp at 80 as it was in their 50s. A paper published in the journal Nature provides a new potential explanation for this discrepancy, and it taps into one of the hottest debates in neuroscience: whether human brains can grow new neurons in adultho