“…Now, the first study of its kind in mice suggests that the brain may clear away that old information in the process of forming new memories.
For the most part, the brain stops producing new neurons—a process called neurogenesis—soon after birth. In humans, mice, and some other species, however, neurogenesis continues throughout life in a brain region that encodes memories about space and events, called the dentate gyrus of the hippocampus. In adult humans, the dentate gyrus produces roughly 700 new brain cells each day.”
“Psychologists have long considered the process of forgetting as key to a healthy mind, yet neuroscientists haven’t paid much attention to it in the past, Frankland says. “If you embrace the idea that forgetting is healthy,” then it makes sense that neurogenesis may contribute to the clearing out of old memories, he says. Although it’s pure speculation at this point, he says, it’s possible that one way that antidepressants help people with depression, a condition linked to reduced neurogenesis, “is to promote some sort of clearing or forgetting,” he says.”
Source: https://www.sciencemag.org/news/2014/05/how-brain-deletes-old-memories