Experts Trick Mind Into Recalling Things That Never Happened In Mice

Neuroscientists have done what Hollywood has glorified for years in espionage thrillers. They have planted false memories in the brains, but of mice. They also found that many of the neurological traces of these memories are identical in nature to those of authentic memories.

Researchers have for long sought the location of memory traces also called engrams. The team from MIT confirmed that memories are stored in networks of neurons that form memory traces for each experience we have. In the latest study, the team from MIT’s Picower Institute for Learning and Memory showed that they could identify the cells that make up part of an engram for a specific memory and reactivate it using a technology called optogenetics.

The researchers engineered mouse’s hippocampal cells to express the gene for channelrhodopsin, a protein that activates neurons when stimulated by light. They also modified the gene so that channelrhodopsin would be produced whenever the c–fos gene, necessary for memory formation, was turned on. They then conditioned these mice to fear a particular chamber by delivering a mild electric shock. As this memory was formed, the C–fos gene was turned on, along with the engineered channelrhodopsin gene. This way, cells encoding the memory trace were "labelled" with light–sensitive proteins.

The next day, when the mice were put in a different unkown chamber, they behaved normally. However, when the researchers delivered a pulse of light to the hippocampus, stimulating the memory cells labelled with channelrhodopsin, the mice froze in fear as the previous day’s memory was reactivated. "Compared to most studies that treat the brain as a black box while trying to access it from the outside in, this is like we are trying to study the brain from the inside out," the researchers said. "The technology we developed for this study allows us to fine–dissect and tinker with the memory process by directly controlling the brain cells".