SSS 2009-11-12（在线收听）

We all love getting something new. But then we have to move around our current clutter to find a place for it. Well, looks like things work the same way in the brain. Because according to a study published in the journal Cell, newborn neurons in the brain’s memory center make room for new memories by moving out the old ones.

Ten years ago, scientists discovered that the brain makes new neurons well into adulthood. These cells arise in the hippocampus, a brain region associated with learning and memory. So everyone figured these new neurons must help make new memories, although no one knew how.

Working with rodents, researchers watched what happens when they either prevented neurons from being born or made them sprout faster. They found that new neurons help move older memories out of the hippocampus and into long-term storage in the neocortex. Such shuffling, they think, may free up space in the hippocampus and increase its capacity for taking in something new. The new memories in the study happened to be fearful ones, but the researchers think the process applies to all memories stored in the hippocampus. Which means your brain is probably moving stuff around right now so you can remember this story.