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Freeing the Mind to Forget

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.

釋放心靈，忘記不快

有些事情很難記住。有些事情——尤其是那些帶來巨大創傷的事情——則很難忘記。不過，有結果發現在忘記糟糕事情方面，小孩子要比成年人做得更好。現在科學 家們認為他們找到了答案。根據發表在9月4日《科學》（Science）雜志上的一項動物研究結果，成年人的大腦會豎立起有形的障礙，使得過去痛苦的記憶 保持原封不動。

對于成年人，那些在情感上擾亂我們的事情易于深深印在我們的大腦內。而且那些記憶能重現出來，從而導致我們焦慮、害怕甚至讓我們患上創傷后精神緊張性障礙 （post-traumatic stress disorder）。但是年輕大腦的“柔韌性”要好的多---它們甚至能抹去那些不快的記憶。

科學家們為了更好的理解這種“年輕的遺忘”現象，他們研究了年輕和年老老鼠的大腦。科學家們發現，在成年老鼠大腦的杏仁核（杏仁核與情感記憶有關）的某些 細胞周圍形成了一種有形的網。科學家對成年老鼠進行了訓練，使得這些老鼠能把輕微的足部電擊和一種特定的聲音聯系在一起，一旦這些老鼠聽到這種聲音，它們 就會退縮。但是當使用一種藥物去掉這種障礙后，這些成年老鼠又恢復了它們消除可怕記憶的能力。因此對老鼠進行“消除障礙網”處理后，當這些老鼠在聽到這種 特定聲音的時候，它們仍然保持安靜的狀態。

這是完全失去變為真正獲得的為數不多的例子之一。

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