SSS 2009-09-04（在线收听）

Some things are hard to remember. Others are hard to forget—especially things that are traumatic. But kids, it turns out, are better than adults at forgetting the bad stuff. Now scientists think they know why. According to an animal study in the September 4th issue of the journal Science, the brains of adults erect physical barriers that keep painful memories intact.

As adults, events that emotionally disturb us tend to get seared into our brains. And those memories can resurface, causing anxiety, fear and even post-traumatic stress disorder. But young brains are much more resilient—and can even erase unpleasant memories.

To get a better handle on this youthful forgetting, scientists studied the brains of young and old rats. They found that in adult brains, a physical net forms around certain cells in the amygdala, a structure associated with emotional memories. Adults that had been trained to associate a mild foot shock with a specific sound would flinch when they just heard the sound. But using a drug to dissolve this barrier restored the older rats’ ability to extinguish fearful memories. So rats that got the net-busting treatment stayed calm when they heard the sound.

One of the few instances where a net loss is a real gain.