In the study of monogamy in prairie voles, scientists applied optogenetics, a technique which uses light to control neurons that have been genetically modified to be sensitive to light. A 2014 study pioneered the use of the tool to switch traumatic memories on and off in mice. How did that work?
The seminal study: Scientists attached light-sensitive markers to memory-associated neurons in male mice and mildly shocked their feet as they crawled in a particular place. Later, the researchers moved the mice to another place, and switched on those same neurons by shining light on them. The mice froze in fear after this triggered a negative memory of being shocked (without the actual shock).
Next, they put the mice in a space with female mice. They activated the neurons again to change the emotional content of the memory and four days later reactivated the neurons. They found the mice no longer froze and instead crawled around with the females. (They also successfully did the inverse.)What happened: The memory of a place and what happened was still there but the researchers were basically able to re-assign an emotion to that context and content.The legacy: The experiment was one of the first to demonstrate how light can be used to precisely manipulate one of the brain's central functions. Optogenetics is now used to probe the brain in myriad ways and some scientists suggest that instead of electrically stimulating neurons, brain-machine interfaces would be better off using light.