illustration by Leif Parsons

Creating False Memories

Many a science fiction movie is based on a person getting “brainwashed” into remembering something that never occurred. But is it really possible to create a false memory? For mice, the answer is yes. HHMI Investigator Susumu Tonegawa made rodents, after being placed in a certain location, recall receiving a mild shock there when, in reality, the event happened in a completely different place.

Memories cause lasting physical and chemical changes in brain cells. A few years ago, Tonegawa and his colleagues used these changes to pinpoint which nerve cells were activated in response to different situations. As a follow-up, they decided to see if they could use this information to create a false fear association in mice.

First, Tonegawa and colleagues at the Massachusetts Institute of Technology identified the nerve cells triggered in mice while they were exploring a new cage. Next, they put the mice in a different cage and applied a mild shock to their paws while stimulating the cells that contained memories of the previous cage. Finally, the mice were placed in the first cage again. They froze in place.

“We got the animal to be scared of an environment where, technically, nothing bad had ever happened to it,” explains Steve Ramirez, a graduate student in the Tonegawa lab. The results were published July 26, 2013, in Science.

Next, the team would like to see if they can introduce pleasurable memories in mice, or memories of objects and other mice.