Can light turn negative memories into happy ones?

Everyone has negative memories, and while time and circumstances can change how severely those memories affect our daily lives, it may be impossible to forget completely. What may be possible, however, is to use light to change fearful memories into happy ones.

According to a new study published in the journal Nature, researchers have been able to manipulate neurons by using light, effectively changing the electrical patterns associated with a fear response. Researchers used laboratory mice and created a fear memory by shocking the mice every time they went to a certain corner of their cage. Eventually the mice became fearful of that corner.

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Once the fear memory had been created, researchers then used light manipulation to affect the firing patterns of neurons associated with it. Once altered, the pathways no longer linked the corner of the cage to the emotion of fear and the mice no longer avoided the area. Researchers were also able to reverse the study, creating a fear response to a memory where there was not one initially.

How did researchers know which neurons to target?

Targeting neuron pathways is not a new technology; it is called optogenetics, and researchers have been experimenting with it for the last few years. What makes this study unique is how experts were able to find and target the neurons responsible for a specific memory.

According to a report from Live Science, researchers found the memory neurons by genetically engineering mice to emit a light-sensitive protein expressed when  neurons created new memories. This light sensitivity is what allowed researchers to turn memories on and off, changing how mice responded in a given situation. They then took it a step further and explored where different memories were stored. Contextual memories, for example, or the memory that cued mice to a certain corner, was stored in the hippocampus where emotional memory, which stored the fear response, was found in the amygdala.

All in all, these findings allowed researchers to only erase the emotional part of a memory, not the contextual part. The mice still remembered the corner of the cage, just not the fear associated with it.

Researchers hope this technology will one day be able to provide therapy for individuals suffering from conditions like post-traumatic stress disorder without having to completely remove memories entirely.

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