In the world of Harry Potter, one’s memory can be manipulated with the flick of a wand. Albus Dumbledore reels wispy memories out of his head and puts them in a Pensieve. If he later dunks his head in that magical basin, he can see his past experiences with lifelike clarity. Hermione Granger, meanwhile, uses the spell “Obliviate” to remove herself from her parents’ memories to protect them from the wizarding world.
In real life, memories are not storable liquids or files that can simply be deleted. Memories are made when a person has an experience that triggers electricity to course through connections between the brain’s neurons. The more exposure to an experience someone has, the stronger the connections become. But they can also weaken over time, leading to forgetting.
The power to make someone perfectly remember or completely forget something is still mere fantasy. But some researchers have taken early steps to strengthen or weaken memory. That work could help people suffering from diseases such as Alzheimer’s or mental health conditions like PTSD.
How to strengthen memory
Neuroscientist Robert Hampson is inspired by Dumbledore’s Pensieve. “I love to see the idea of being able to pull a memory, store it, look at it, examine it,” says Hampson, of Wake Forest University School of Medicine in Winston-Salem, N.C.
He and colleagues haven’t found a way to store past experiences like leftovers in magical dishes. But they have found that applying electric zaps to the brain could help people form stronger memories.
The team recorded electrical activity in the hippocampus — a brain structure involved in memory — of nine people with epilepsy who had brain implants. As the volunteers took a picture-based memory test, the team documented neuron-firing patterns linked to seeing specific images.
Next, the group applied tiny electric zaps that mimicked those patterns to the hippocampus in eight other volunteers as they took the same memory test. Those participants’ memories for images paired with the small jolts improved by 35 to 40 percent. Their memory did not improve for pictures not paired with zaps.
In the future, brain implants might deliver tiny zaps to help boost memory in people with Alzheimer’s or brain injuries, Hampson says.
How to weaken memory
Other scientists are looking into whether it’s possible to help people forget certain memories.
Experiences can change how neurons connect to each other. Changes in these connections encode, or store, the memory of the experience, many researchers think. But “you can interfere with that encoding,” says neuroscientist Samuel Schacher of Columbia University.
His team studied neurons from mollusks called sea hares: Two sensory neurons each connected to the same motor neuron, which controls muscle movement. Each connection is moderated by a different form of a molecule called PKM. By stimulating these cells in lab dishes and inhibiting one type of PKM molecule, the team could selectively block a connection without affecting the other. The findings hint that it’s possible to erase some memories while leaving others intact.
Someday, new therapies might coax human neurons into letting go of unwanted memories. That would be useful for treating PTSD, in which traumatic memories cause the mind to link a neutral experience to a dangerous one. “But you don’t want to erase the fact that other behaviors associated with the bad event may be useful to remember,” Schacher says.
The ethics of manipulating people’s memories “are very thorny,” says André Fenton, a neuroscientist at New York University. Our lived experiences — and memories of them — make us who we are. Changing a person’s memories could, in some ways, cause them to be a different person, he says. “We must proceed very carefully.”