All of us have memories we'd rather forget. The dream of being able to erase our recollection of our most painful moments is now looking more realistic thanks to a new technique that, under highly controlled conditions, weakens recall of stories that arouse a negative response.

The science of understanding how we store memories is in its infancy, unable to explain why some things stick and others don't. Early theories proposed memories are initially flexible and easy to disrupt, but become harder to shift after consolidation.

Recently, however, some psychologists have found evidence that animals' fear responses can be disrupted long after they have taken hold. To see if this extends to humans, Professor Bryan Strange of the Polytechnic University of Madrid had participants watch a slide show while listening to two stories, each with a tragic or violent mid-section.

A week later, participants had their memory of one, randomly chosen, story reactivated by being shown part of the first slide and asked questions about it. The participants were then given propofol, a strong but short-acting general anesthetic, sometimes with adjuvant agents. Either 24 hours later, or as soon as they had recovered from the anesthetic, they were tested on their recall of each part of both stories.

Anesthetics interfere with memory formation, so people often forget what happened shortly before going under. The participants tested immediately after recovery remembered the two stories equally well (within expected margins of error). The anesthetic canceled out the memory-enhancing effect of having the one story brought back to the surface.

However, in Science Advances Strange reveals something much more remarkable.

Those who were tested after 24 hours were much less likely to remember the mid-section of the story that had been reactivated than the one that was not reactivated. Memories of the beginning and end of the two stories were equally clear.

Thus even long after a memory is thought to have become well-established, it could be made to lose some potency.

Although this sounds very Eternal Sunshine of the Spotless Mind, propofol is not something to be taken lightly. Strange would have struggled for ethics approval for this test, were it not that the participants all needed anesthetics for gastroscopies or colonoscopies, and Strange piggy-backed on the medically necessary procedure. Even if memory deletion by anesthetic becomes a new form of therapy, you probably wouldn't undergo it to forget a sad break-up, let alone to clear your brain of that time you made a fool of yourself in front of your crush.

On the other hand, for people traumatized by time in a war zone or childhood abuse, the technique might soften the PTSD-inducing memories, making it easier for people to recover their lives.