The persistence of memories

Looking into the recent scientific discovery of erasing memories and the ethics of its application to humans

For many scientists, the prospect of the ability to erase fearful memories in human brains is considered one of the ‘Holy Grails’ of the field of memory work.
For many scientists, the prospect of the ability to erase fearful memories in human brains is considered one of the ‘Holy Grails’ of the field of memory work.

In the 2004 movie Eternal Sunshine of the Spotless Mind, Jim Carrey and Kate Winslet star as two ex-lovers who opt to have their memories erased after their relationship turns sour. Nominated for two Academy Awards, four Golden Globes and a Grammy, the film’s concept of erasing traumatic memories seemed to be complete fiction. But groundbreaking research at Toronto’s Hospital for Sick Children is showing the script may not be entirely fictitious.

Human brains are filled with countless memories, many as vivid as if they had happened yesterday. Some people live with the burden of traumatic memories like car crashes, war or abusive relationships. When they close their eyes they don’t find themselves smiling at the past, but rather frozen with terror. A group of researchers from Toronto’s Hospital for Sick Children have succeeded in erasing brain cells that store fearful memories in mice, offering positive transcendence in the hopes of erasing traumatic memories in humans. Senior Scientist for Neurosciences and Mental Health Dr. Sheena Josselyn and her team of research scientists, have identified what they claim to be “one of the Holy Grails” of memory work—the fear-storing neurons in the research mice are located in the same amygdala region as in humans. The original premise came from scientist Karim Nader—professor of neuroscience at McGill University—whose work on reconsolidating memory inspired the premise of Eternal Sunshine of the Spotless Mind.

Josselyn said the region involved in storing fear memories possesses high levels of a protein known as CREB, otherwise known as the universal memory protein, which is essential in the process of memory formation. Researchers were able to selectively stimulate these specific fear-storing neurons by introducing a virus that triggered CREB memory machinery and turned the cells on. Josselyn said her interest lies in the ways the human brain encodes and stores memories.

“We modeled the human memories using mice, conditioning them to store fearful memory through Pavlovian techniques,” she said. The lab mice were administered a mild shock paired with a tone similar to a bell. One occurrence was enough to condition these mice, because the next time they heard the tone they froze—a species-specific type reaction to fear. Using a combination of genetics, viruses and toxins, Josselyn and her team were able to surgically ablate the few cells that encoded the fearful memory while leaving the rest of the brain intact. Josselyn said the experiment didn’t destroy the brains’ entire capacity to remember fear, but rather only the specific recollection of the shock. “Although the sights and sounds [of the original incident] remain, it is the fear associated with such that is eliminated. We can always re-learn this fear.”

In an interview on March 13 with the Toronto Star, Dr. Michael Salter, head of the neurosciences and mental health program at Toronto’s Hospital for Sick Children, said this discovery doesn’t necessarily mean this procedure should be carried out on people.

“In humans, one wouldn’t want to kill these neurons,” he said. “And certainly it’s not feasible to do it by this technology because you’re not going to inject diphtheria … viruses [into people].”

Although the possibility of administering toxins into a human brain are far from plausible and wouldn’t be accepted in the medical world today, Josselyn said she thinks her team’s discoveries have incredible implications on the future of trauma treatment. “Our research has given amazing insight into how the brain works. It is truly amazing how something that happens once can be imprinted for your entire lifetime … [T]his discovery offers the suggestion that we do not have to treat the entire body to overcome trauma. Many trauma patients spend years in therapy trying to overcome their experiences. These developments offer the possibility of developing a smart drug that could possibly target just those neurons associated with the retention of traumatic experiences.” For decades, the idea of memory alteration has intrigued society. From concepts of totalitarian societies and mind control in George Orwell’s Nineteen Eighty-Four to movies involving the idea of brainwashing, it’s understandable why society would be apprehensive towards these new scientific breakthroughs. However, if approached with caution, Josselyn said these new discoveries could provide endless solutions. The painful memories of violent occurrences that lead to post-traumatic stress disorder have the capability to ruin a person, leaving an individual a shell of what they once were. “Painful memories are a good thing, they teach us life lessons which cause us to grow,” Josselyn said. “We only want to touch that hot stove once. We want those memories of pain—they protect us from future harm. Our research intention is not for the cosmetic uses of impaired lives, but this research has the capability to make a whole lot of people a whole lot happier.”

As with any controversial scientific discovery, the invasiveness and extent of the procedure can be called into question. Could one erase the memory of a bad break-up? Although some would argue that memories of past relationships are traumatic, Josselyn said she disagrees. “I heard somewhere that much of great art and music only come out of suffering,” she said. “It can’t all be good. We should have a balance of memories, the good and the bad.”

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