Passage 6 Drug-free Memory Erasure Could Lead to Spotless Minds 068
“删除记忆”疗法 《新科学家》2009-12-10

[00:00]A new drug-free therapy wipes away fearful memories in rats and humans.
[00:08]The simple treatment might eventually help patients
[00:12]with post-traumatic stress disorder (PTSD), say researchers.
[00:19]The new procedure relies on a quirky property of memories called reconsolidation.
[00:27]The process of jogging a memory - with an emotional or sensory jolt,
[00:33]for instance - seems to make it malleable for a few hours.
[00:40]Potent drugs that block brain cells from making new proteins
[00:46]can erase fearful memories during this window. But these chemicals are toxic,
[00:53]and wholesale memory erasure could do more harm than good, says Karim Nader,
[01:01]a neuroscientist at the McGill University in Montreal, Canada.
[01:07]In search of a gentler way to block fearful memories, Marie Monfils,
[01:14]a neuroscientist at the University of Texas in Austin,
[01:19]tweaked a therapy sometimes used to treat PTSD, called extinction.
[01:27]Previous studies in patients and animals suggest that extinction therapy
[01:35]works up to a point, but fearful memories often reappear,
[01:41]Monfils says. She and her colleagues wondered if performing extinction
[01:49]during the reconsolidation window might lead to a permanent effect.
[01:55]Her team first taught rats to associate a musical tone with a slight electric shock.
[02:03]Playing the tone with no shock generally causes rats to freeze in fear.
[02:12]When her team played the tone over and over again, 19 times, the rats displayed less
[02:21]and less fear. This is standard extinction therapy. However,
[02:27]a month later their fear of the tone returned, strong as ever.
[02:34]To make the effect permanent, Monfils team jogged other rats'
[02:40]memories of shocks just once, waited an hour for memory reconsolidation to begin,
[02:48]and then played the tone over and over.
[02:52]"It's very simple and almost na?ve to think it would work,
[02:58]" Monfils says. But the fearful memories disappeared permanently.
[03:05]Rats that got extinction therapy after this reconsolidation window
[03:11] had closed relapsed as well.
[03:15]Monfils theorizes that extinction therapy alone creates two parallel memories
[03:22]linked to the tone or blue square, one fearful, one not.
[03:29]Waiting for reconsolidation to kick in overwrites the original memory
[03:35]instead of making a parallel memory, she says.
[03:40]Despite proof of principle experiments in rats and humans,
[03:47]Monfils says researchers should proceed with caution
[03:51]in applying the new findings to treating PTSD or other anxiety disorders.
[04:00]Some people's reconsolidation windows may be longer than others,
[04:06]and people respond differently to stressful situations.