33. How to Erase a Single Memory

By Susan Kruglinski|Friday, December 28, 2007

We have all forgotten things, but what if we could choose to erase a particular memory from our consciousness? A memory of childhood abuse, say, or the imprint of a violent death? In March, neuroscientist Joseph LeDoux and his colleagues at New York University took an important step toward memory manipulation when they “erased” specific memories from the brains of rats.

In the experiment, LeDoux and his team planted two separate traumatic memories in the rats’ brains. The memories were in the form of sounds (a siren and a beep), each paired with an electric shock. The researchers later replayed the sounds, forcing the rats to retrieve the memories. When playing back the beeping sound (without a shock) for half the animals, the team administered the enzyme inhibitor U0126 directly into the rats’ amygdala, a section of the brain associated with emotion. The next day, when both sounds were played, the rats who had been given the drug were fearful of the siren but not of the beep, suggesting that the beep-plus-shock memory was blocked.

Because the rats cannot communicate the details of their experience, it is difficult to say exactly how the drug affected those memories. Did a full erasure take place, or did the rats simply lose their emotional connection to the stimulus? “In the rat, we are testing implicit memories, memory that you don’t need conscious awareness for,” says LeDoux. “A human would have a cognitive memory of that experience. We don’t know if these manipulations will affect cognitive memory or if they will just affect the emotional memory.”

The research may contribute to the development of medication that helps reduce the impact of traumatic memories and post-traumatic stress disorder in humans.

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