We all have a dubious memory or two that we are convinced is real, even if it never happened. For some the memory is harmless, like the song that played during a first kiss. For others, like courtroom witnesses convinced they saw a suspect only to have their account overturned later by DNA testing, the strange whims of memory can result in real-world disaster.
Which is why a new experiment by neuroscience researchers at MIT's Center for Neural Circuit Genetics is equal parts important and terrifying. Writing in the journal Science, Nobel laureate Susumu Tonegawa outlines how he and his team were able to plant false memories in the brains of mice, tricking them into believing in events that never actually occurred.
The technique they employed is called optogenetics, which allows researchers to manipulate individual brain cells with near-pinpoint precision using a tiny, fiber-optic beam of light. As Ars Technica notes, optogentics "has brought surprising technical advances and changed the way many neuroscientists work."
[Researchers] engineered brain cells in the mouse hippocampus, a part of the brain known to be involved in forming memories, to express the gene for a protein called channelrhodopsin. When cells that contain channelrhodopsin are exposed to blue light, they become activated. The researchers also modified the hippocampus cells so that the channelrhodopsin protein would be produced in whichever brain cells the mouse was using to encode its memory engrams.
In the experiment, Tonegawa's team placed the mice in a chamber and allowed them to explore it. As they did so, relevant memory-encoding brain cells were producing the channelrhodopsin protein. The next day, the same mice were placed in a second chamber and given a small electric shock, to encode a fear response. At the same time, the researchers shone light into the mouse brains to activate their memories of the first chamber. That way, the mice learned to associate fear of the electric shock with the memory of the first chamber. [Guardian]
Then, when researchers placed the mice back in the first chamber, the mice responded in a way that clearly communicated fear: They froze.
"We call this 'incepting' or implanting false memories in a mouse brain," Tonegawa tells Science.
What does that mean for human memory formation? Admittedly, not much for now. At that level of brain activity, "the difference between a mouse and a human are quite small," Edvard I. Moser, a neuroscientist who was not part of the experiment, tells the New York Times. "[But] what I find fascinating about this is that you actually can point to a physical substrate to memory," or an engram. It's like pointing to a specific spot in the brain, and being able to say, "That is the memory."
If the thought of being implanted with a fake memory creeps you out, that's totally understandable. But Tonegawa says his research isn't malicious, Inception-inspired Noltan-ites be damned.
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