美科学家发现新疗法 清除改写记忆或将成真

Roadside bombs, childhood abuse, car accidents—they form memories that can shape (and damage) us for a lifetime. Now, a handful of studies have shown that we’re on the verge of erasing and even rewriting memories. The hope is that this research will lead to medical treatments, especially for addiction and post-traumatic stress disorder (PTSD).

Researchers have known for decades that memories are unreliable. They’re particularly adjustable when actively recalled because at that point they’re pulled out of a stable molecular state. Last spring, scientists published a study performed at the University of Washington in which adult volunteers completed a survey about their eating and drinking habits before age 16. A week later, they were given personalized analyses of their answers that stated—falsely—that they had gotten sick from rum or vodka as a teen. One in five not only didn’t notice the lie, but also recalled false memories about it and rated that beverage as less desirable than they had before.

Studies like these point to possible treatments for mental health problems. Both PTSD and addiction disorders hinge on memories that can trigger problematic behaviors, such as crippling fear caused by loud noises or cravings brought about by the sight of drug paraphernalia.

Several studies have found chemical compounds that can be used to subdue or even delete memories in mice (and maybe someday in people). In June, a report led by an Emory University researcher showed that SR-8993, a drug that acts on the brain’s opioid receptors, can prevent a fear memory from forming. Researchers strapped mice to a wooden board for two hours—a stressful experience that later gave them a heightened sense of fear similar to PTSD. But mice given SR-8993 before or after the stressful incident were less likely to end up this way.

Another study identified a drug, Latrunculin A, that can erase memories days later. The researchers trained rodents to consume methamphetamine in an environment with distinctive visual, tactile, and scent cues such as black walls, gridded floors, and the scent of vanilla or peppermint. Rodents that were injected with Latrunculin A two days later didn’t seek out meth when returned to that environment, but others did.

To make more targeted treatments, researchers will ultimately need to understand how the brain’s neurons encode each memory. Last year, Susumu Tonegawa at the Massachusetts Institute of Technology reported that individual memories in mice leave telltale molecular signatures in the brain’s hippocampus region. In July, his group caused mice to falsely associate an old memory with a new context—essentially creating a false memory.

The idea of scientists manipulating memory does, naturally, sound a bit creepy. But it also points to some possible good: treatment for millions of people tormented by real memories. And that’s something worth remembering.

路边炸弹、童年受虐、惨烈车祸……这些可怕的场景会成为记忆，然后带来一生的阴影。据美国媒体报道，现有研究显示清除甚至改写记忆即将成为可能，这将为医治上瘾和创伤后应激障碍（PTSD）等心理病症提供一种全新的治疗方法。

早在几十年前，科学家就发现记忆是不可靠的。尤其当人们主动唤起某种记忆时，该记忆被迫脱离一种稳定的分子状态，进而变得更加容易调整。去年春天，美国科学家公布了在华盛顿大学进行的一项研究成果。在此研究中，多名成年志愿者就其16岁之前的饮食习惯填写调查问卷。一周后，他们各自收到一份个性化分析报告，其中故意加入他们年少时曾因饮用朗姆酒或者伏特加酒而患病的内容。然而令人意外的是，1/5的志愿者不仅没有察觉到报告中的错误，他们还回想起当时并不存在的糟糕场景。并且，这些志愿者与之前相比，变得对酒水饮料更加没有兴趣。

诸如此类的研究为治疗心理健康疾病提供了一个全新的视角。包括上瘾和创伤后应激障碍在内，类似的心理疾病都与能够激发问题行为的记忆紧密相关，例如噪音会使患者感到恐惧、看到吸毒用具则会勾起毒瘾。

还有一些研究发现，化合物可以被用来抑制甚至消除老鼠的负面记忆。今年6月，美国埃默里大学的研究人员发布了一篇研究报告，报告称一种名为“SR-8993”的药物可作用于大脑中的阿片样物质受体，从而阻止形成恐惧记忆。实验过程中，研究人员把老鼠捆绑在木板上长达两个小时，对于受试老鼠而言，这是一种可怕的经历，它们会产生类似创伤后应激障碍的心理恐惧。而服用了“SR-8993”药物的老鼠，产生恐惧心理的几率比没有服用药物的老鼠要低。

另一种名为“拉春库林A”的药物，则能够在事后清除记忆。在这个实验中，科学家对受试老鼠进行训练，令其一旦处于特定的幽闭环境就会食用冰毒。两天后，受训成功的老鼠被注射了“拉春库林A”药物，当它们被再次放入幽闭环境时，却没有食用病毒。而那些没有注射的老鼠则如常食用。

为了令治疗方法更具针对性，科学家还需要了解掌握大脑神经元究竟是如何生成记忆的。去年，麻省理工学院教授、1987年诺贝尔生理或医学奖得主利根川进发现，老鼠的个体记忆会在大脑海马区留下分子标签。今年7月，利根川进研究团队成功在老鼠的旧记忆与新内容间建立起虚构的联系，从本质上讲，这相当于创造了一个虚假的新记忆。

由此看来，尽管操纵记忆听上去有些令人毛骨悚然，但科学家的这种尝试是有益的：因真实记忆而备受折磨的数百万心理疾病患者或将因此痊愈。