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Some years ago, scientists successfully introduced a “memory” into a sea slug by implanting it with some ribonucleic acid (RNA) from another sea slug that had the original experience. The experiment illustrated one of several mechanisms involving memory in living organisms, though it’s still a long way from, say, the movie Total Recall where Arnold Schwarzenegger’s character buys an artificial memory of a vacation he can’t afford (Colin Farrell in the 2012 remake—both movies are adaptations of the Philip K. Dick short story “We Can Remember It For You Wholesale”).

However, recent research has brought a team of scientists closer to that capability. First, the researchers trained mice to associate an electric shock with a specific odour. They carefully observed which neurons in the mouse brain were stimulated by these activities. Then, using a technique called optogenetics, they used light to stimulate equivalent neurons in the brains of other mice, creating a “memory” in mice that had never experienced either the shock or the odour themselves.

Other research has shown that the most robust memories get their vividness and durability because they involve multiple neurons encoded the same way. You can easily see how this would happen when experiences are repeated lots of times, like when we practice skills to train ourselves, or actively memorize certain information. But particularly powerful experiences can produce a similar result. The more neurons involved in the memory, the better it’s able to withstand the loss of a neuron or two through aging or other malfunctions. Also, as with groups of former high school buddies who get together to reminisce, the slightly different information contributed by each of them produces a more accurate, fleshed-out whole. (Though we sometimes remember the same events very differently!)

The many processes involved in making, storing, and retrieving memories are still not well understood. Some neuroscientists will insist that memory storage in our brains is fairly nebulous, involving electrical potentials more than hard and fast artefacts of information. They’ll say that there’s no place in your brain where a picture of your first pet exists, although you can probably remember every line of its furry face (or think you can). Having been a radio broadcaster for decades, there are popular songs I’ve heard hundreds of times and, though I probably couldn’t recreate the recordings note for note, I can at least easily tell when I hear a remix or re-recording of a song even if it’s by the original artist. The singer holds a certain note a fraction longer, or the sax riff is played on an instrument with a slightly different tone than in the original. I have tunes playing in my head most of every day, no Spotify required. Maybe I don’t have a library of mp3s stuffed somewhere in my head, but the experience is pretty close to that. No wonder there’s no room in there for remembering to take out the garbage!

Because memory is such a critical part of our identities and how we perceive the world around us, the prospect of copying, erasing, altering, or replacing our memories is a disturbing one, which no doubt explains why the subject has appeared so often in science fiction. From the 1880’s when Edward Bellamy wrote Dr. Heidenhoff's Process about a doctor who could remove unwanted recollections, the subject of “memory editing” has been a staple of the genre. Getting rid of traumatic or otherwise unwanted memories is an obvious subject to explore, often used in military SF (the equivalent of joining the Foreign Legion) and, in the interest of an exciting plot, it usually goes wrong. Eternal Sunshine of the Spotless Mind is a great movie example. Erasing memories as a way of protecting secrets is especially common, utilized by the Mule in Asimov’s Foundation series, the Utopia-dwellers in Clarke’s The City and the Stars, the Strangers in the movie Dark City and the special agents of Men In Black, among many others. Memory erasure by aliens is an absolute given in UFO mythology!

Less common is the concept of actually inserting memories of experiences that never happened, like in Total Recall or the 2010 movie Inception (visually stunning and exciting, even if the science is non-existent)—this is more the territory of thrillers involving “brainwashing”, like The Manchurian Candidate. But the prospect of remembering things that may not have happened might be even more disturbing than losing memories. It not only calls our sense of identity into question, but the very knowledge of what is real and what isn’t.

A better understanding of how memory works could be a godsend to an aging population facing the increasing risk of Alzheimer’s disease and other dementias, and offers hope for those suffering brain injuries. We can readily believe that removing, or at least weakening, traumatic memories could be therapeutic for many troubled people. And artificially “remembered” skills or knowledge could be genuinely useful and save a lot of time. But it’s just as easy to imagine the frightening misuses such technology could be put to, as often seen in dystopian stories about authoritarian governments seeking to control the minds of the masses. Innovators in business or technology could be tricked into revealing vital secrets to competitors, or national security operatives fooled by hostile nations. Political leaders could be manipulated by enemies, or even just suspected of being controlled—the results of either could be devastating.

On the individual level, a victim of a tragic life might be given an invented past of happiness and fulfillment instead, allowing them to live the rest of their lives in contentment. Yet every struggle they’ve undergone, every achievement they’ve made, would be rendered meaningless.

As with so many areas of scientific advancement, the knowledge we’re gaining can be invaluable, but its value is in how we make use of it. That’s also where the pitfalls lie. And they are many.