“If mice had Hollywood, this would be ‘Inception’ for them,” said one of the lead researchers, MIT neuroscientist Steve Ramirez, whose study was published online Thursday in the journal Science.
Ramirez and his colleagues tagged brain cells associated with a specific memory and then tweaked that memory to make the mouse believe something had happened when it hadn’t.
Although implanting a memory won’t happen anytime soon in people, in principle, it should be possible to isolate a human memory and activate it at will, scientists said.
“We would have every reason to expect this would happen in humans exactly as it happened in mice,” said Michael J. Kahana, who was not involved in the study but is director of the University of Pennsylvania’s Computational Memory Lab.
Researchers said the ability to implant a false memory was a scientific milestone; Kahana called it a “technical tour de force.” The study’s authors said this type of research could one day help treat some emotional problems, such as post-traumatic stress disorder, which involves the intrusion of unwanted memories.
The first step in the mouse experiment took place last year when Ramirez and his colleagues isolated an individual memory in a mouse’s brain by tagging the brain cells associated with it and inducing recall of the memory at will by forcing those neurons to fire with light. In this new study, they artificially stimulated neurons to make associations between events and environments that had no ties in reality and, in essence, implanted a new, false memory.
They used a technique called optogenetics, which uses light to turn on and off activity of individual brain cells in a living animal. An optical fiber feeds light into the mouse’s hippocampus, the area of the brain that plays a prominent role in forming new memories.
False memories in humans often happen when a person swaps out one detail for another. Sometimes these mistakes are trivial, such as swearing that you left your keys on the kitchen table only to find them hanging in the garage. In a courtroom setting, a false eyewitness account can destroy an innocent person’s life.
Ramirez recounts a true story about an Australian psychologist who was arrested for a rape he did not commit. Physically, he fit the bill of the victim’s description, but he had a foolproof alibi. He was speaking on a live television show at the time of the rape — the same show, it turned out, the victim had been watching right before her attack. As a result, she described him as her attacker, even though it wasn’t possible.
Red room equals danger
In their experiment, the scientists implanted memories associated with certain rooms or chambers where they placed the mouse. Similar to a person visiting a friend’s apartment and forming a memory about his ratty couch and cramped bathroom, a mouse explores and takes mental note of a given chamber’s nooks and crannies.