You will remember… FEAR!

Science News chills us to the bone with the latest breakthrough from Mark Mayford and Susumu Tonegawa, neuroscientists at Scripps and MIT, respectively. They’ve been able to manufacture memories – terrifying memories of things that never happened – in mice:

Though the two teams used different approaches, they both created a false memory of a fearful situation in mice. In the work reported in Science… Mayford and colleagues relied on a molecule that, upon binding a particular drug, could activate nerve cells. The team genetically engineered the mice so that only the nerve cells active during the formation of a particular memory would make the molecule.

The marked memory was of a square room with opaque white walls and floor, and no particular odors. The mice played in this room, had their memory tagged and later went into a different room — this time, a wintergreen-scented room with a black-and-white checkered wall and a gridded floor. Here, the animals were subjected to shocks.

In some of the trials, the researchers reactivated the memory of the white room during the shock session. This taught the mouse to associate the combination of the reactivated memory and the scented room with a shock, forming a hybrid memory. Sure enough, in later trials, these mice froze only when researchers placed the mice in the second room and simultaneously reactivated the artificial memory.

The study in Nature, led by Susumu Tonegawa of MIT, labeled and recreated a fearful memory in mice using molecules that respond to certain kinds of light, a technique called optogenetics. A day after the fearful experience, in an entirely different room, the animals froze in fear when the light was turned on and the artificial memory was called to mind. This flash of light “led to the entire recall of yesterday’s terrible experience,” says Tonegawa.

Stimulating a small number of nerve cells led to a complex behavioral response.