We often view our memories as something fixed, like exhibits in a museum, to help us understand who we are today and what the future might hold. Recent studies, though, indicate that memories are more like well-used library books; every time we revisit them, they shift and change a little.
Take a moment to think of a happy memory. Really engage with it. Picture the scene and try to rekindle some of the joy or excitement you felt then. Give it a minute or two. If you did this, believe it or not, your brain and body underwent some changes in that brief time.
As you started reflecting on that memory, neurons that were quiet just moments ago sprang into action, sending chemicals flying to each other. This activation lit up brain regions tied to emotions, which explains why you might’ve felt similar emotions surface. If you were feeling stressed before, you probably noticed your heart rate calming down as stress hormones like cortisol decreased. If you were already relaxed, it’s possible your heart rate quickened with excitement.
In both situations, parts of your brain associated with rewards released dopamine. That memory didn’t just change you; you also altered the memory itself in the process, according to neuroscientist Steve Ramirez. Some aspects of that memory became more prominent, while others faded. Your current mood influenced the memory, as neurons responding to how you felt syncopated with those related to the memory itself.
Every time you revisit that cherished moment, you reshape it, impacting both your experience of it and the physical connections in your brain.
This two-way street of memory alteration has been part of human experience for ages. However, over the last twenty years, researchers have discovered astonishing methods to manipulate memories (at least in mice). These include implanting false memories, erasing real ones, reviving memories lost due to brain injuries, and even swapping emotional responses from one memory to another.
Ramirez emphasizes that this symbolizes a broader scientific shift toward making memory manipulation a common practice in labs. In his recent book, he asserts that while a memory can transform a person, individuals have the ability to reshape their memories too—both mentally and scientifically.
In stories about memory manipulation, there’s often a sinister scientist portrayed. Yet, Ramirez, who teaches at Boston University, is down-to-earth. He even has a giant inflatable dinosaur named Henry decorating his office. He envisions this research not as a tool for mind control but as an avenue to alleviate mental distress, complementing existing medications and therapies.
He expressed his amazement at the capabilities of modern neuroscience—though he sees the ultimate aim as restoring health and well-being to individuals. He views memory manipulation as another potential remedy in the therapeutic toolkit.
Ramirez’s personal connection to memory runs deep. His father was once kidnapped in El Salvador, falsely labeled a guerrilla fighter. He was spared when a captor recognized him as a kind classmate who used to share his lunch.
Before Ramirez’s birth, his parents emigrated to the U.S. and raised him and his siblings in Boston. He earned a neuroscience bachelor’s at Boston University in 2010 and a PhD from MIT in 2017, where he teamed up with a celebrated researcher and a fellow postdoc, Xu Liu.
Both were inspired by the potential of memory to serve as a therapeutic tool, forming a close friendship and partnership in their lab work. Their breakthrough arrived in 2012.
A team from the University of Toronto had shown that certain neurons became active when a mouse heard a sound previously paired with a shock. They then eliminated those specific neurons, rendering the mice unresponsive to the sound. If memories could be erased, Ramirez and Liu speculated, then perhaps they could implant memories too.
They identified brain cells in a mouse’s hippocampus that activated during an alarming stimulus. By transferring the mouse to a new environment, with no signals linking to the flashback, they could stimulate those cells with pulses of light, evoking an experience without the actual stimulus.
Behaviorally, the mouse reacted as if the shock had occurred, indicating a successful memory activation.
Years later, they placed a mouse in a new box, while noting the brain cells that activated. Then, they moved it to a smaller cage alone. Initially, the mouse seemed downcast, but when Ramirez and Liu reactivated the cells linked to positive social interactions, the mouse perked up, choosing sugary water over water without sugar. This change, brought on by recalling happier moments, showcased the potential of memory recollection to influence behavior.
The results of their research, published in 2015, marked a significant achievement, yet it was bittersweet; Liu passed away unexpectedly just as the paper was being reviewed.
Ramirez reflects on grief and memory as closely interlinked: both persist through our lives, shaping who we are.
Opening his own lab at Boston University in 2017, Ramirez has since witnessed impressive advances in memory research. Scientists are reestablishing memories lost to amnesia, activating memories while minimizing associated emotions, and more.
That said, there isn’t an anticipation that doctors will wield lasers to reshape human memories anytime soon. The experiments are confined to genetically modified mice equipped with light-sensitive neurons, and altering humans in that way is deemed unethical and impractical by researchers.
Moreover, it may not even be necessary. Scientists understand that humans are quite suggestible, and our memories can be easily influenced without technological interference. The real aim of this research, Ramirez argues, is to uncover the biological mechanics of memory to apply that knowledge towards noninvasive therapies.
By grasping how to promote memory retrieval in cases where damage has occurred, there may be potential applications for individuals suffering from cognitive disorders. Understanding how memories and their emotional responses are encoded could lead to breakthroughs in treating conditions such as PTSD.
Of course, there’s a troubling aspect to this line of inquiry: the same insights that could enhance well-being might be misused. Ramirez points out that the notion of artificially altering memories could give rise to fears of a dystopian future—a world where identities are erased or manipulated by governing powers. However, he insists that any tool can be employed for good or ill, and he’s more focused on fostering beneficial advancements.
In essence, he believes that ethical memory manipulation could become just another therapeutic approach among other remedies for brain health, like exercise and adequate rest. “What if memory tweaking could also serve a purpose for healing? Then we’re making real progress,” he concludes.
