Painful memories could be erased, new study says

The horrors of war, the torment of childhood trauma, the distress of being victimized by violent crime it may be possible to erase these recollections from our brains.

Scientists have taken another step toward being able to edit out bad memories while leaving good ones intact something that could one day be used to treat people suffering from post-traumatic stress disorder (PTSD)or anxiety disorders linked to painful memories.

You might be able to erase different aspects of the memory. WayneSossin,Montreal Neurological Institute

Previous research has found that memories are not as stable as once thought. One chemical process recalls a memory,and a different one stores it, but that process can be blocked, and the memory lost.

"Depending on how youremindthe person, you might be able to erase different aspects of the memory,"said Wayne Sossinof the Montreal Neurological Institute and Hospital atMcGillUniversity,whose lab collaborated with researchers at the Columbia University Medical Center in New York.

It didn't work out so well in Eternal Sunshine of the Spotless Mind, a movie in which two aggrieved lovers undergo a procedure to wipe one another from memory, but traces remain and they find each other again.

The new research doesn't go as far as picking specific memories or peopleto erase, but it shows that different types of memories can be discerned and targeted, even when they are stored within the same neuron.

"One might have thought there was a unified process where memories were maintained that you couldn't erase one without erasing them all," Sossintold CBC News.

'Could be promising'

Sossin and his colleagues set out to reverse the storage of two kinds of memories:

• associativea link learned from experience, such as being mugged in a dark alley.
• non-associative linksarising from conditions peripherally related to the experience, such as being in a city at nighttime, where one can expect there to bedark alleys.

They speculated that both the strength and the retention of different types of memories were governed by variants of an enzyme called PKM.

The researchers induced, with electrical stimulation,both types of memories in a molluscand found they could erase memories separately by targeting the PKM variants. Their paper was published June 22 in the journal Current Biology.

"We do it by interfering with different molecules,"Sossinsaid. "We identified molecular targets that were specific for associative and non-associative memory."

• How childhood trauma can have a life-long impact on health
• Chances are your memories are untrue and unreliable, says criminal psychologist

The two types of memory can be distinguished on a molecular level; though it would bemuch more difficult to pinpoint an exact recollection say, running through a meadow versus running through a war zone.

But if it can be done, one mental health expert sees potential for this technique.

"Where I think it could be promising is in these instances of more acute trauma if someone was involved in a robbery or other violent crime of some kind, for example," said Mark Henick, national director of strategic initiatives at the Canadian Mental Health Association.

He said there is evidence that intervening in the immediate aftermath of a traumatic event can reduce the likelihood of developing PTSD later, "if you can effect the memory before it becomes ingrained."

However, Henick said, psychologicaltrauma is, in many cases,not the result of one isolatedevent, asin the case of a child who's abused for years.

"How do you erase a lifetime? Arelationship? How do you erase someone's father from their lives?"Henicksaid. "Or you look atintergenerationaltraumainAboriginal communitieshow do you erase someone's ancestry?We know that stress and trauma can be passed biologically."

And trauma is often more complex, involving "overgeneralizations" beyond the event itself. Anxiety rooted in the memory of a gunshot can be triggered by the sound of fireworks, or a car backfiring, for example.

Negative memories stronger

That's where the ability to target associative and non-associative memories could be useful.

"In general, negative memories are stronger than positive, and they are more apt to bring along additional unrelated [non-associative] memories that wouldn't normally get associated with the event or the fear," Sossin said.

But one doctor who specializes in treatingpeoplewith PTSD worries about what her patientsmight be losing besides a memory.

"A lot of people can experience post-trauma growth," said Dr. Vivien Lee, a clinical psychologistat the Centre for Addiction and Mental Health in Toronto. "They work through it and grow as a person, they become a better version of themselves. Adversity is what makes us grow as individuals."

• Health system should recognize intergenerational trauma, expert says

She also foresees the potential for a slippery slope.

"My concern would be that people would start doing that for any kind of negative [memory]," she said.

Sossin also said he would have some reservations about removing memories rather than letting them evolve, as they inherently would.

"New experiences changes your view of something," he said. "You want memories to be able to be updated."

Besides, he says, science is "a long way" fromusing electrical manipulations this way on people. For now, it's only in movies.