You know that scene in Eternal Sunshine of the Spotless Mind when they're scanning through Jim Carrey's playdoh-faced head, looking for bad memories to erase? A bunch of eggheads from MIT just figured out how to do that for real! Sort of. In all seriousness, though, the discovery is poised to do a lot of good for sufferers of post-traumatic stress disorder.

The gene in question is known as Tet1, and it controls memory by manipulating the levels of DNA methylation (read: altering access to genes). To test how Tet1 affects memories, the researchers conditioned mice that had been shocked by a particular cage to be fearful. After a while, they'd put the mice back in the same cage—without the shock—and record their reactions. Mice with normal Tet1 levels would eventually forget about the shock, letting new memories replace old ones. Mice with low Tet1 levels, however, had a hard time forgetting.

The low Tet1 levels could be key to understanding conditions like post-traumatic stress disorder, a condition that's continued to baffle medical researchers. If doctors could find a way to raise those levels in, say, soldiers returning from battle, they might be able to let positive memories erase the trauma. It would actually give the soldiers more agency.

"What happens during memory extinction is not erasure of the original memory," says Li-Huei Tsai, director of MIT’s Picower Institute for Learning and Memory. "The old trace of memory is telling the mice that this place is dangerous. But the new memory informs the mice that this place is actually safe. There are two choices of memory that are competing with each other."

In other words, bringing up Tet1 levels could help a person decide what to remember and what to block out. Turning this research into an actual treatment plan for PTSD patients is probably a few years down the road—after all, the scientists are still testing it out on the mice. But it's exciting that we're learning how to forget. Now if we could only figure out how to remember… [MIT]