The neuroscientist working on ‘zapping’ away unwanted memories

Think of your happiest memory. A wedding, your child’s birth, or maybe just a perfect night out with friends. Sit with it for a moment. Remember the details. What were you wearing? What did it smell like? How did it make you feel?

Now do the opposite. Think of a sad memory—the loss of a loved one, getting laid off, or a painful breakup. Sit with this one too.

Which would you rather keep? 

Of course, you want the happy memory, the one that made you feel good and joyful about life. Yet, the painful ones linger for years and sometimes decades, like bruises beneath the surface. If you could choose, would you keep them—or delete them entirely?

If this is all starting to sound like something out of Eternal Sunshine of the Spotless Mind or Inception, you wouldn’t be too far off—and Steve Ramirez would agree with you. Ramirez is a neuroscientist at Boston University and National Geographic Explorer whose research occurs on the bleeding edge of memory science. He’s perhaps best known for studies he helped conduct that showed that it was possible to implant a false memory in mice. The findings were published in the journal Science in 2013 and the Royal Society in 2014. 

His research is built on a central truth: Memory is fickle. It changes and morphs every time we recall it. Ramirez compares it to hitting “Save As” on a Word document. Everytime we retrieve a memory, we change it slightly. Ramirez is exploring whether we can harness that “Save As” process—intentionally rewriting our memories instead of letting them change by accident. So far, he’s figured out how to do something even more surprising: not destroy a bad memory, but create a new one.

The science of remembering what never happened

“We know memories are malleable, and susceptible to modification,” says Ramirez. “Every time they’re recalled, they’re being saved and edited with bits and pieces. We wanted to see if we could do that in the lab. Because if we could do that directly in the lab and brain, then we can really get a higher resolution snapshot of how memories work when they’re being warped or when they’re being modified.” 

The team’s foundational study came in a 2012 paper published in Nature where they identified and activated a cluster of neurons in mice brains that encoded a fear memory—specifically, a mild foot shock. To do so, the researchers genetically engineered the mice so that memory-related neurons become light sensitive. The creatures were then placed into a box and received a foot shock—resulting in the memory of that shock becoming encoded in the light-sensitive brain cells.

The team then surgically implanted a tiny fiber-optic cable into the skull of each mouse that they could use to shine a laser into its brain. When they turned it on, it activated the bad memory on command like flipping a switch.

Next they wanted to see if they could create a false memory. For this, they put a mouse in a safe box and let it explore. The next day, they placed the mouse in a different box, triggered the memory of the safe box by shooting a laser over its brain, and simultaneously gave it a foot shock. When they later returned the mouse in the first box, it froze in fear—even though it never received a shock in that box. 

The team had, in effect, implanted a false memory in the mice.

“The key thing with that experiment was that we showed that we could artificially activate a memory while the animal was experiencing something. Later, that new, updated version was the animal’s last recorded version of that memory,” he explains. “The mouse was scared in an environment where, technically, nothing bad happened.” 

Inside the brain’s editing room

Between the lasers, false memories, and shocking experiments, you’d be forgiven if you thought this was getting pretty sci-fi. Ramirez embraces the comparison as his work often brushes up against science fiction in big ways. 

“I think science fiction and science reality are in lockstep, often influencing each other in surprising and unpredictable ways,” Ramirez says. “What sci-fi can get ‘wrong’ sometimes is inevitable, but the work it inspires and the dreams and visions sci-fi can conjure up in people is practically limitless, and I love it for that very reason.”

Still, it can seem scary, especially when you consider the potential applications to humans. But Ramirez says that memory manipulation would take a decidedly less invasive approach for people—no brain lasers required. Instead, if you want to activate a happy memory in another person, all you have to do is ask them about it. (Remember the beginning of the story—or did you forget?) 

“We can update a seemingly safe memory into something negative,” he says, referring to the foot shock test. “But what about the opposite: Can we turn a negative memory into a positive memory?”

Despite the pop-culture comparisons to Inception or Eternal Sunshine, Ramirez’s real-world applications are far less cinematic—and arguably more profound. Instead, his work is laying the groundwork for helping people with PTSD process harmful memories, or those with neurodegenerative disorders like Alzheimer’s and dementia live longer, better lives. 

In a forthcoming paper currently under peer review, his team claims they were able to identify where exactly a memory will form in the brain days before it even happens. It’s like being able to predict where lightning is about to strike before the storm even gathers. This might allow future clinicians to anticipate the effects of Alzheimer’s, Parkinson’s, and dementia before they occur. 

“Imagine being able to make a Google Maps for memory, but with the level of individual brain cells,” he says. “You could say, ‘This is a positive memory in the brain. It’s located here in this 3D web of activity. We can zoom into it here and it looks like something is misfiring, and that might be the remnants of some kind of cognitive decline or memory loss, or amnesia, or Alzheimer’s.’” 

We’re still a long way away from a Google Maps for memory. However, Ramirez is quick to point out that his field of research is still in its infancy. He puts it this way: the study of neuroscience is roughly 100 years old—whereas physics is more than 2,000 years old. “Relative to physics, neuroscience is still in its Pythagorean Theorem stage,” he jokes.

There’s still a lot we don’t know about the brain and, as a result, how memory works. But Ramirez and neuroscientists like him are turning science fiction into science reality, which may allow us to one day edit and manipulate our own experiences. More importantly, their research helps us understand the profound ways that memory shapes us—and how we might begin to shape it right back.

This article is part of Your Memory, Rewired, a National Geographic exploration into the fuzzy, fascinating frontiers of memory science—including advice on how to make your own memory more powerful. Learn more.