When my late lab partner Xu Liu and I first lit the brain cells that held certain memories felt as if you were seeing a thought come back to life. We stimulated a constellation of neurons within the mouse hippocampus and hypothesized that these neurons were the physical basis of the memory, or engram. We didn't realize that we were entering one of the most exciting frontiers in neuroscience: the ability to edit memory itself.
The phrase “memory manipulation” has an ominous ring to it, conjuring up dystopian visions of erased history or perpetuated lies. But in the laboratory, the reality is softer and much more encouraging. The same discoveries that allow us to turn memories on and off in mice teach us how to heal the brain from withinincluding how to relieve traumatic memoriesenhance fading those and balance the emotions that our memories carry.
Over the past decade, this work has revealed three main principles. First, memories are malleable when stored, recalled, and retrieved. Second, they are distributed throughout the brain rather than in one area. And third, they can be artificially etched into the brain. Each principle redefines what “memory editing” actually means.
When we form memories, brain cells fire together and strengthen their connections. This process can be enhanced or weakened by different stimulation patterns. Brain stimulation using implanted electrodes or magnetic pulses can improve navigation virtual environments. Drugs, hormones, or even a little sugar can improve the brain's ability to stabilize new experiences. And exercise stimulates the growth of new neurons and improves the health of our hippocampus, the rest of the brain, and the entire body. body. The same idea works vice versa. Overstimulation of memory circuits and memory power fades; block the molecules that cement these bonds, and they weaken even more.
Memories can also be altered when recalled, temporarily destabilizing the memory and opening a window of opportunity before it is stored again. Therapists are already using this “window of reconsolidation” when helping people living with phobias or trauma. In our animal studies, repeated reactivation of negative memories is sufficient to blunt their emotional charge. Moreover, reactivating positive memories during stress can completely overwrite the negative tone. IN miceA week of “positive memory reactivation” reversed depressive behavior for more than a month.
Because memories are distributed throughout the brain, they are also surprisingly durable. Damaging one area rarely removes the entire experience. Instead, the brain may redirect access through alternative pathways and cause several “drafts” memory. This redundancy offers hope for treating Alzheimer's disease: if we can strengthen the still intact pathways to memories, we may be able to restore parts of the self that were once thought lost. Thus, memory manipulation is not about rewriting who we are, but about giving the brain new ways to return to itself.
The idea raises ethical concerns, just as every major medical advance ever did, from pacemakers to transplants. The goal of our work is to reduce suffering and thereby improve our collective well-being: to help a veteran loosen the grip of a memory, someone in recovery to separate a craving from its trigger, or someone with Alzheimer's to hold on to the names of loved ones.
Learning to modify memories responsibly can help us heal, and the brain already edits memories every time we revisit them. Science today simply studies the rules. And when I think about the flashing memories of Xu, I don't see science fiction. I see scientific facts and a future in which memories become medicine for the mind.
Steve Ramirez is the author How to change memory: one neuroscientist's attempt to change the past
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