Creating False Memories in Mice

A mouse associated the negative experience from one box with the positive environment of another.

The idea of implanting memories has been a staple of science fiction for decades, dating back to Philip K. Dick's We Can Remember It for You Wholesale, which became the Arnold Schwarzenegger movie Total Recall. Now researchers are closer to producing false memories in the brains of mice.

The technique could lead to treatments for phobias and post-traumatic stress disorder in humans. "It shows that the stuff from movies like Inception or Total Recall is possible," said graduate student Steve Ramirez, of the RIKEN-MIT Center for Neural Circuit Genetics in Cambridge, Mass. He and his colleagues, led by Susumu Tonegawa, reported their findings in this week's issue of the journal Science.

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To give false memories to mice, the researchers started by engineering a benign virus to infiltrate cells and unload a gene that directs the cell to produce a protein called channelrhodopsin-2. From previous studies, the researchers knew that the protein stimulated cellular activity -- in this case, memories -- when exposed to light.

They injected the gene-toting virus into a part of the mouse's brain called the hippocampus. This region is where new memories of day-to-day activities, called episodic memories, form and are stored. The formation and storage of memories occurs when certain proteins in the brain change slightly. Based on research the team did last year, they knew which hippocampal cells to target with light.

To illuminate the cells, the scientists inserted a thread-thin fiber optic cable into the mouse's brain.

Next, they put a mouse into box called environment A and dubbed it the "safe" zone. In this box, the mouse was allowed to move about in a normal way for about 10 minutes. The mouse ran around and explored, acting generally calm.

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The next day the scientists put the mouse in another box called environment B. At that point they pulsed light through the fiber optic cable and flashed the brain cells that produced the channelrhodopsin-2 protein. This stimulated a memory. At the same time they gave the animal a mild shock to its feet.

"Here, we were trying to artificially make an association between the light-reactivated memory and the foot shocks. We were just trying to artificially connect the two," Ramirez said.

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