Bad Memories Could Be 'Erased'


The war veteran who recoils at the sound of a car backfiring, and the recovering drug addict who feels a sudden need for their drug of choice when visiting old haunts have one thing in common: Both are victims of their own memories. New research indicates those memories could actually be extinguished.

A new study from MIT found a gene called Tet1 can facilitate the process of memory extinction. In the study, mice were put in a cage that delivered an electric shock. Once they learned to fear that cage, they were then put in the same cage but not shocked. Mice with the normal Tet1 levels no longer feared the cage once new memories were formed without the shock. Mice with the Tet1 gene eliminated continued to fear the cage even when there was no shock delivered.

A gene could aid in memory extinction and bring to life a real "Eternal Sunshine of the Spotless Mind."

“We learned from this that the animals defective in the Tet1 gene are not capable of weakening the fear memory,” Le-Huei Tsai, director of MIT's Picower Institute for Learning and Memory told Discovery News. “For more than a half century it has been documented that gene expression and protein synthesis are essential for learning and forming new memories. In this study we speculated that the Tet1 gene regulates chemical modifications to DNA.”

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The MIT researchers found that Tet1 changes levels of DNA methylation, the process of causing a chemical reaction. When methylation is prominent, the process of learning new memories is more efficient. When methylation is weaker, the opposite is true.

“The results support the notion that once a fear memory is formed, to extinguish that memory a new memory has to form,” Tsai said. “The new memory competes with the old memory and eventually supersedes the old memory.”

Experts in the study of memory and anxiety agree.

“This is highly significant research in that it presents a completely new mechanism of memory regulation and behavior regulation,” said Jelena Radulovic, a professor of bipolar disease at Northwestern University. The mechanism of manipulating DNA is likely to affect many other things. Now the question will be whether there will be patterns that emerge, whether there will be side effects on moods and emotions and other aspects. But the findings have real relevance.”

Radulovic, who was not directly involved in the study, says the primary significance of the findings have to do with eliminating fear.

“The results show us a very specific paradigm of learned reduction of fear,” she said. “This could mean that interference with the Tet1 gene and modification of DNA could be an important target to reduce fear in people with anxiety disorders.”

For her part, Tsai is most encouraged at the ability to approach anxiety disorders at the molecular and cellular levels inside the brain. “We can now see the bio-chemical cascade of events in the process of memory formation and memory extinction,” said Tsai. “Hopefully this can lead to new drug discoveries.”

Meanwhile, research in memory extinction is progressing quickly, largely due to new discoveries through traditional experimentation, augmented by advances in technology, Tsai said.

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