“Remembrance of things past is not necessarily the remembrance of things as they were.” —Marcel Proust
Proust was on to something. As powerful as our memories may be, they’re certainly not infallible. Our minds lead us astray all the time, but experts hadn’t gotten to the root of the brain’s deceptiveness—until now.
Scientists at the Massachusetts Institute of Technology say they have successfully implanted a false memory in a mouse, giving insight into how memories—true and false—may form in the human brain. Led by Susumu Tonegawa (a Nobel laureate for his work in immunology), the team reported Thursday in the journal Science that they caused genetically modified mice to remember being shocked in a particular place when, in reality, that electric shock was delivered when the mouse was somewhere else entirely. Here’s Susan Young, writing for Technology Review:
Previously, the MIT-based team had shown that it could pinpoint the location and assemblage of cells that carry a memory, and that activating those cells stimulated memory recall in mice. To create the new, false memory, Tonegawa’s team reactivated a mouse’s memory of a safe place while the animal received shocks in its feet, thus transforming the original memory.
First, the team used genetic tricks to label the brain cells involved in the memory of a chamber that was safe and neutral. The next day, they put the animal in a second chamber, a completely different setting. There, the animal got foot shocks while the researchers simultaneously shone light to reactivate the memory of the harmless first chamber. When the animal was put back in the first chamber, it fearfully froze—a clear indication that it remembered getting shocked in that chamber, even though that never happened.
James Gorman wrote in The New York Times that although mice and people are evolutionarily distant, the processes that govern memory formation in mammals are ancient. In both mice and men, memories form in an area of the hippocampus called the dentate gyrus—so conclusions drawn from this study are likely to apply to humans as well. Moreover, the scientists’ ability to locate and edit a memory is a significant achievement. Gorman quotes Edvard I. Moser, a neuroscientist at the Norwegian University of Science and Technology:
“What I find fascinating about this,” Dr. Moser said, “is that you actually can point to a physical substrate to memory,” what the researchers call an engram. Neuroscientists have long talked about engrams, but Dr. Moser said the recent research is the closest they have gotten to pointing to a spot in the brain and saying, “That is the memory.”
Of course, researchers have long known that memory blurs fact and fiction. But this new discovery is an important step toward figuring out how that actually works. Writes Alok Jha for The Guardian:
The mouse models created by the MIT team will help scientists ask ever more complex questions about memories in people. “Now that we can reactivate and change the contents of memories in the brain, we can begin asking questions that were once the realm of philosophy,” said Steve Ramirez, a colleague of Tonagawa’s at MIT.
Learn more about mice and memory by watching this NOVA scienceNOW episode. (Skip ahead to Chapter 2, which begins at 17:07.)