Researchers have known for decades that memories are unreliable. They're particularly adjustable⁵ when actively⁶ recalled because at that point they're pulled out of a stable molecular⁷ 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 beverage⁸（饮料） as less desirable than they had before.

 

Studies like these point to possible treatments for mental health problems. Both PTSD and addiction disorders⁹ 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（随身用具，设备）.

 

Several studies have found chemical compounds that can be used to subdue¹⁰ 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 strapped¹¹ 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 erase¹² memories days later. The researchers trained rodents¹³ to consume methamphetamine in an environment with distinctive¹⁴ visual, tactile¹⁵（触觉的）, and scent¹⁶ cues such as black walls, gridded floors, and the scent of vanilla¹⁷ or peppermint¹⁸. 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（海马） region. In July, his group caused mice to falsely associate an old memory with a new context -- essentially¹⁹ 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 tormented²⁰ by real memories. And that's something worth remembering.

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