“Mammals’ brains make new cells throughout life — a process called neurogenesis — but babies of some species, including humans, produce new neurons at a much higher rate. And this process is particularly active in the hippocampus, which deals with memories and learning.
Most of the time, neurogenesis leads to better learning and improved memory. But there’s a catch. According to the Science paper, the extremely high rates of neurogenesis seen in very young brains can actually increase forgetfulness. These new neurons could be crowding out the old circuits that hold memories.”