Have you ever recalled a memory and wondered if it actually happened? It sounds like something from a science fiction film, but a team of neuroscientists from MIT have demonstrated an ability to implant false memories into mice brains.

A study published today in Science reports the team’s findings. Along with the ability to create fictitious recollections, the researchers also discovered that, neurologically speaking, traces of the false memories are dead ringers for authentic memories.

These memory traces are known as “engrams” to neuroscientists, and the locations of these engrams have been of interest to researchers for quite some time.

In the past, Susumu Tonegawa, senior author of the paper, and her team have identified cells from an engram for particular memories, and they have been able to reactivate those particular memories using a technology called “optogenetics.” This technology enables neurologists to selectively turn cells on or off using light.

To plant memories in mice, Tonegawa and her team used channelrhodopsin, a protein that activates neurons when it is stimulated by light. The cells in the hippocampus of the mice were engineered so that they would express the gene for channelrhodoposin. Whenever a gene necessary for memory formation (c-fos) was turned on, channelrhodoposin would be produced.

Research scientist Xu Liu said:

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 technology we developed for this study allows us to fine-dissect and even potentially tinker with the memory process by directly controlling the brain cells.”

The experiment proceeded as follows:

  • Day 1: the researchers put the mice in chamber A and allowed them to run around freely, meanwhile labeling their memory cells with channelrhodopsin
  • Day 2: the researchers put the mice in chamber B, which was quite different from chamber A. Eventually, the mice were shocked mildly on their foot while researchers activated the memory cells from chamber A with light
  • Day 3: the researchers put the mice back in chamber A.

When the mice were placed back in chamber A on the third day, they “froze in fear,” even though they were never shocked there.

The reason why the mice feared the memory of chamber A is that the researchers implanted a false memory of being shocked in it. In effect, the mice were reliving the memory of being in chamber A while they were being shocked in chamber B, and therefore now feared chamber A.

The researchers note that the false memory they implanted in the mice seemed to compete with the real memory of chamber B. Though the mice also froze when they were placed in chamber B, they did not freeze quite as much as those mice that received a chamber B shock without having chamber A memories activated.

Anyone who watched the 2010 sci-fi thriller Inception starring Leonardo DiCaprio will understand that there are serious implications involved with having the ability to alter human memory. And the scientists are already planning future studies around how memories can be altered in the brain.

But the research team from MIT is optimistic about how these findings may help people in the future. Lead author Steve Ramirez says:

Now that we can reactivate and change the contents of memories in the brain, we can begin asking questions that were once the realm of philosophy.

Are there multiple conditions that lead to the formation of false memories? Can false memories for both pleasurable and aversive events be artificially created? What about false memories for more than just contexts – false memories for objects, food or other mice?

These are the once seemingly sci-fi questions that can now be experimentally tackled in the lab.”

For now, we can relax knowing that our memories are own. Those that we remember, anyway.