A Mechanism for Selectively Erasing Memories Holds Promise

Researchers erased certain memories from slug neurons, opening up the possibility that this could one day work on humans with memories that trigger anxiety or awaken trauma.

If you had the chance to erase your worst, most painful memories, would you do it?

New research published in the journal Current Biology by neuroscientists from the Columbia University Medical Center (CUMC) and McGill University suggests that this may someday be possible, bringing us closer to the reality of manipulating the recollection of our pasts.

Basically, by deactivating the proteins that have encoded memories into your brain, you could theoretically restore the neural state that preceded a traumatic memory. Not only would you forget what happened, but your brain wouldn’t even have the infrastructure to recall the memory anymore.

Memories are believed to form at neural synapses, the sites where electrical impulses are passed back and forth between neurons. Changes in these neural synapses can both strengthen and weaken memories. Protein kinase M molecules (PKM) are an essential part of memory formation that can be activated by external stimulation, such as a traumatic event.

“They amplify whatever the external signal was to create internal change that can last from minutes to decades,” Samuel Schacher, a professor of neuroscience at CUMC and co-author of the study, told Seeker.

These PKMs are guarded by another protein, KIBRA, that allows them to remain constantly active — thereby keeping a memory alive. But the research team’s findings show that a disruption either to the PKMs or the KIBRA proteins that protect them can produce a partial or complete memory erasure.

“When the activity of this [PKM] molecule is inhibited, the synaptic strength returns to its previous value and the memory is erased,” said Wayne Sossin, a neuroscientist at McGill and another member of the team, in an email.

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But not all memories are the same. The researchers discussed two types of memories in their paper: associative memories and non-associative memories.

Schacher likes to give the following example: You’re cutting through a dark alley in a high-crime neighborhood when you suddenly get violently mugged. You see a mailbox sometime during or immediately following the assault. You might have two residual sources of fear: dark alleys, and mailboxes. One of those fears — which links the dark alley with the risk of crime — is associative. That’s a good memory to have, because it may make you more wary. But the fear of mailboxes — the non-associative memory — isn’t important, and could hinder you in the future.

Such incidental non-associative memories, Schacher said, might be helpful to have erased.

The scientists conducted the experiment in a petri dish by shocking a neural circuit from the sea slug Aplysia, an animal that is commonly used in neuroscience research because of its relatively simple nervous system. They found that both associative and non-associative memories exist separately in the same neuron, and that they could selectively erase either type by disrupting the PKM molecule.

The fact that associative and non-associative memories are distinct means that you could turn off the harmful, non-associative memory of an event while keeping the helpful associative memory.

The memories could either be partially erased or completely erased, Schacher said, though the processes that would determine this are not yet clear. That’s what’s next for the researchers: figuring out what proteins would trigger partial erasure (so that the memory could still be recalled if prompted), or full erasure (no memory whatsoever).

Theoretically, if this were better understood, a drug or treatment could be developed that would allow selective memory erasure in humans.

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Not all neuroscientists, however, believe that complete memory erasure is even possible. Several years ago, a group of researchers from the UCLA Integrative Center for Learning and Memory conducted a similar experiment and erased memories from Aplysia neurons. But they found that despite the appearance that the memories were completely erased, they persisted “covertly.”

“What these results imply is that at least some elements of long-term memory may be quite resistant to current methods of memory ‘erasure’,” David Glanzman, an author on that trial, wrote to Seeker via email.

There are some ethical dilemmas to consider. The researchers don’t predict that the technology would go into full-on Eternal Sunshine of the Spotless Mind territory, in which a broken-up couple undergo a procedure to have the relationship wiped from their minds, though Schacher acknowledged that he “can see where the comparison might be.”

“Our identities are very tied to our memories,” Sossin said. “I would imagine that erasing a memory in a human would have a ton of ethical issues.”

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But the prospect of such ethical qualms shouldn’t mean that examining the neurological underpinnings of memory isn’t worth pursuing.

“I understand the cautionary notes associated with this,” Schacher said, “but I still think it has important value.”

In their research, the authors noted that memory erasure could be a significant help to people combating with severe anxiety or PTSD. It could also possibly be used to combat forms of addiction.

There’s one large caveat, however: despite the presence of some similar proteins, the neural circuits of slugs are vastly different from the complexities of the human brain. “Many studies in rodents and probably non-human primates would need to be done to determine how specific the erasure could be” before testing the technology in humans, Sossin noted.

Glanzman doesn’t think testing in humans is even possible right now. With current technology, he explained, such a study “would be extremely difficult, and perhaps impossible, to perform in the mammalian brain” due to the small size of our neurons.

Though we’ve taken a step closer, we’re still some ways off from the era of memory erasure in humans.

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