• More Blogs
• Observations »
• Bering in Mind »
• Cross-check »
• Extinction Countdown »
• Solar at Home »
• Expeditions »
• Guest Blog »
• Anecdotes from the Archive »

In the movie Eternal Sunshine of the Spotless Mind, Joel and Clementine's relationship ends so sourly that the couple elects to have their mutual memories swept away via a non-surgical procedure called "targeted memory erasure." No such tool actually exists. Even the most intense therapies can't completely erase troubling or fearful memories in adults. Yet, if two young rats fall in and out of love—or, more likely, have a close encounter with a subway car—permanent memory erasure may actually be possible, previous research has suggested. So, what happens in a growing rodent brain to cause this change?

A new study on mice uncovers some answers that could someday offer a potent target for eliminating the recurrence of bad memories in humans, especially known to those who suffer from post-traumatic stress disorder (PTSD).

"Fear memories are the most robust memories—they can last over a lifetime," says Nadine Gogolla, a biologist at Harvard University and lead author on the paper published today in the journal Science. "You can push them far back, but spontaneous recovery and relapses will happen." Until now, science has been unable to stop this process—in humans or in mice. 

By repeating the previously reported rat findings, Gogolla and her colleagues found that at some point during a young mouse's development—between about 16 and 23 days postnatal—a molecular net of sorts is cast over a region of the brain called the amygdala, effectively crystallizing formerly malleable memories.

"It looks just like what you would expect from a fisherman's net," says Gogolla of the protein matrix under the microscope. "And it acts as a structural constraint on the cells. How it does that, nobody really knows." But the result is that memories are held inside. 

What the researchers did learn was that by cutting that net—with an injection of an enzyme that digests the chains linking the matrix together—memories could be once again destabilized.

"The drug cuts the net into its pieces," Gogolla says, "just like when you cut the strings of a net and it falls apart." Then, for a couple weeks, the original youthful plasticity in the neuronal circuits of the amygdala is regained and any bad memory formed after the matrix digestion could be subsequently eliminated through "extinction" therapy, a common treatment during which a patient is presented with the original fear trigger but in a context that is not fearful. When the treatment was given after a mouse underwent fear conditioning, however, extinction was unable cut out that memory completely.

"Because the treatment has to occur before a traumatic event, it's hard to make it immediately available," notes Gogolla. "But it does help us in finding the underlying mechanisms." Eventually, she hopes tools can be found that can be applied after fear-inducing experiences, and that translate from mice to humans. This would be welcome relief for the approximately 20 percent of all military personel who have returned from Iraq and Afghanistan reporting symptoms of PTSD, not to mention for heartbroken couples.

Also see our podcast on this research.

Picture by Don89 via iStockphoto

2 Comments

1. 1. mo98 06:54 PM 9/7/09

   The lingering silence after an authoritarian lecture seems to be enforced with the remark: Any Questions? Somewhere along the line, those asking too many questions challenge stereotypes. The neural fishnet seems to be nature's mechanism to let first encounters kick in hard and ensure survival of both students and faculty. With electronic information exchange, such things as post traumatic stress disorder treatment within virtual environments may cause entire societies to rethink how we are raised. Curiosity doesn't kill experienced survivors precisely because memory doesn't get erased completely. Perhaps research in concepts presented in the movie MATRIX apply namely to the amygdala and in practice would allow the brain to program itself thereafter without taboos grounded in fear.

   Reply | Report Abuse | Link to this

2. 2. MZFreedom 12:54 PM 9/10/09

   Why spend time trying to come up with "tools can be found that can be applied after fear-inducing experiences, and that translate from mice to humans."? Why not study techniques that are already known to be effective in humans n neutralizing the emotional content of traumatic memories, such as EMDR and other so-called energy techniques? Oh, I forgot. The goal is to come up with a DRUG that shareholders can reap the benefit of, not a procedure that is fast and effective.

   Reply | Report Abuse | Link to this