Consciously shelved, but forever worming their way – unbidden – to the surface, many of us have no choice but to endlessly re-live moments we’d rather forget. If you could, though, would you uproot some of your memories, selectively erasing past trauma?

While it’s not possible – quite yet – to book an appointment and have such crippling recollections lipo-ed from your brain, neuroscientists are already confident that they can modify and erase selected memories. A slew of studies confirms that one group of memories is particularly vulnerable to chemical redaction: those that relate to the most primal of all emotions – fear.

In one recent example, researchers at the University of California taught mice to fear a certain high-pitched tone by jolting them with a small electrical charge each time it was played. Eventually, even when no shock was delivered, the mice froze in fear whenever they heard that particular tone, while ignoring similar, but lower-pitched, sounds.

The mice came from genetically-modified stock, enabling researchers to monitor the pathways between the part of the brain that registers sound and the amygdala, the emotional centre of the brain. These neural maps – “like a bundle of phone lines”, according to the study’s co-author, Jun-Hyeong Cho – showed that the pathway associated with the high-pitched tone was stronger than that triggered by the low-pitched tone, reflecting the intensity of the fear response.

By repeatedly exposing the same mice to the high-pitched tone without administering any shocks, they were then able to remove that fear. This process – fear extinction – could potentially help humans overcome their own greatest fears, but only if they are willing to have their memories tampered with.

The Californian study, along with several related examples, owes a huge debt to research conducted at Montreal’s McGill University back in 2000. It was then that Professor Karim Nader, a neuroscientist attached to the university’s psychology department, found that it was possible to alter a memory by administering a beta-blocker at the exact moment that memory was recalled.

The tests, again conducted on mice, clearly demonstrated that the simple act of recalling a memory makes it malleable. Given the right circumstances and equipment, any such memory could be reconstituted, with certain elements – fear, for instance – forever erased.

Perhaps ironically, Nader’s research was to prove particularly memorable. Hollywood screenwriter Charlie Kaufman used a number of the professor’s theories as the basis for Eternal Sunshine of the Spotless Mind (2004), his futuristic take on lost loves and rewired recall.

As it turns out, real life may not be far behind such fictional extrapolations. According to Steve Ramirez, an Assistant Professor of Neuroscience at Boston University, many of the ideas showcased on the big screen by Eternal Sunshine – as well as in a number of other similarly-themed movies, such as Inception and Total Recall – could soon be features of everyday life. Chillingly assessing the possibility, he said, “This is a matter of when it happens, not if…”

Echoing his sentiments, Christine Denny, an Assistant Professor of Clinical Neurobiology at Columbia University, said, “While it may seem like science fiction, in our labs, we are now turning memories on and off every day.”

Denny’s approach was to use optogenetics – a technique that uses light to control the behaviour of cells – to map the specific memories of several mice. This test group was then genetically modified and given an injection that made cells light-sensitive. This allowed certain memories to be recorded and then switched on and off through the application of laser beams.

This saw the researchers identify a “happy” memory from back when the mice were roaming around in a safe, dark environment, which they then activated when the test group was suddenly deposited in an unfamiliar and brightly lit box. Although previously petrified and motionless, they began scurrying around happily as soon as the switch was flipped.

In one of Denny’s more recent studies, memories were reawakened in mice suffering from a condition analogous to Alzheimer’s. Although her work is at an early stage, it is hoped that, one day, it could work the same miracle among human subjects similarly afflicted.

Studies such as these have provided hope that there might one day be a viable method of treating phobias, post-traumatic stress disorder and dementia-related syndromes. Within Amsterdam University’s Department of Experimental Clinical Psychology, for instance, Professor Merel Kindt has been using a similar approach to help patients overcome their phobias.

This sees sufferers given propranolol – a betablocker – immediately after their “fear memory” has been triggered, the point at which the memory is most vulnerable to modification. The pill then acts to block the release of noradrenaline – the so-called “fight or flight” chemical – with the fear absent when the memory is reconstituted.

As a sign of its effectiveness, one patient with a debilitating fear of spiders was soon happily stroking a tarantula. “It’s like touching a hamster,” he was subsequently reported as saying.

While such results sound impressive, some have been less than convinced. For her part, Elizabeth Phelps, the Julius Silver Professor of Psychology and Neural Science at New York University, has been unable to match Kindt’s results in lab tests.

Phelps said, “We’ve tried, but we can’t replicate Kindt’s study. To me, it says that the whole thing remains a little messy, while there are clearly a number of areas that we really don’t understand.”

At present, we can merely speculate if the ability to select and delete specific memories will ever become a reality. It may not be too long, though, before we find ourselves wondering if it already has.

Text: Emily Petsko
Images: AFP

For the full article, please check out the latest issue of Gafencu’s print magazine or the PDF version on the Gafencu app. Download the app from the Google Play Store or Apple App Store