A new study demonstrates that it is possible to “reconsolidate” the memories of mice using low-power lasers, in effect rewiring mice memories to an opposite emotional state. The study, a write up of which was published in the August 27th issue of Nature, involved teaching mice to fear or enjoy a specific area of their large cage and then applying laser light light to reconsolidate the memories. After the laser treatment, the mice who used to fear that area were no longer afraid, and the mice that used to like that area were now afraid of it.

Rewiring Mice Memories

Ethicists point out, however, that there are serious ethical issues involved in manipulating human memory remain, even for therapeutic purposes. They point out that means medical science is still a long way from translating this research to clinical interventions, especially since human traumatic memory conditions such as PTSD are much more complex than in mice.

More details on rewiring mice memories

Researchers in this study were looking at whether you can selectively change one part of a memory, that is, the emotion attached to a memory. The method involved creating fearful memories for male mice by giving them electrical shocks, or creating pleasant memories by letting them spend time with female mice.

Then, through a process called optogenetics using laser light to control the activity of brain neurons, the researchers brought back the fear memories every time the mice went to one corner of their cage, which eventually caused the mice to avoid that corner. The researchers used the light to re-evoke the positive memories in the mice with pleasant memories to make one corner attractive to the rodents.

In the final step of the experiment, the researchers reversed the associations between a place and an emotion by evoking only the “place” part of the fearful memories, while allowing the mice to interact with females. This meant the mice were immediately no longer afraid of that particular corner of the cage.

The researchers were also able to do the opposite, and turn positive memories to fearful ones, according to the study.

Statements from MIT researcher

“Recalling a memory is not like playing a tape recorder,” said Susumu Tonegawa of the Massachusetts Institute of Technology, who led one of the studies in a press conference on Wednesday. “It’s a creative process.”

Tonegawa went on to explain the key results of the experiment. “We could switch the mouse’s memory from positive emotions to negative, and negative to positive.”