Forgetting Everything: Coming Soon
Sometimes things happen to us that we wish we could forget. Unfortunately, we can’t control our memory—there’s no way to erase memories at will, like deleting files from a hard drive. But what if memory could actually be intentionally modified? While science fiction has long explored the dangers of such power, real science seems to be getting close to letting writers test their theories in reality.
Our memories largely define who we are, especially episodic memory—the kind that stores the events of our lives and all the twists and turns of our personal stories. It constantly reminds us of who we are and who we used to be. But here’s the problem: we don’t always want to be who we are. Almost everyone has moments in their life they’d rather forget. Some experiences can even lead to post-traumatic stress disorder (PTSD), which often torments war veterans and accident victims. Is it possible to erase these memories?
How Memory Works: Not Like a Diary
If you think of a diary or notebook as a good metaphor for memory, think again. Research shows our memory is nothing like written text or video recordings. Instead, it’s a soft, dynamic structure of associations and feelings, which gets rewritten every time we recall something. Complicated? Of course! The brain itself is an incredibly complex object—almost 100 billion neurons with trillions of connections, controlling the body and creating our inner world. Evolution didn’t stop there; it also gave us a real time machine, letting us mentally revisit the past and relive it.
On the molecular and cellular level, we have some idea of how memory works, but understanding it on the scale of the whole brain is much harder. It’s also tough to give a universal definition that fits both the entire brain and each individual neuron. We can’t even say exactly where memory “lives”: almost all structures of the cerebral cortex are involved in recalling memories. So, precisely and completely removing a specific memory seems nearly impossible, even in the distant future.
It’s even harder to imagine methods that would let us do what the characters in “Eternal Sunshine of the Spotless Mind” did—erasing memories of a specific person. Such memories are a complex web of associations and emotions. But becoming like the character in the series “Homecoming,” who was given drugs after returning from Iraq to erase traumatic war memories and restore combat readiness, may soon be possible. A recent publication in the journal Science Advances discusses research that sounds like a prequel to a five-hour story about a psychologist’s troubled conscience, played by Julia Roberts.
The Role of the Hippocampus and Amygdala
It’s now clear that the hippocampus plays a crucial, if not key, role in forming and recalling episodic memory. The classic view is that it acts as a temporary storage—an information hub needed for both forming and recalling memories. Damage to the hippocampus often leads to episodic memory disorders. A striking example is Kent Cochrane, the famous patient K.C., who lost both hippocampi and could no longer remember events from his life or recall facts about his biography. Interestingly, other types of memory, like semantic memory (knowledge about facts and how the world works), remained almost untouched.
So, removing the hippocampus to treat PTSD is a terrible idea. But could we influence it pharmacologically to prevent a memory from forming, or ideally, destroy it altogether? It turns out there are several approaches to this problem.
We all know that emotionally charged, especially frightening, events are remembered very well. The main culprit is the amygdala, which is next to the hippocampus. In stressful, survival-critical situations, its adrenoreceptors are activated by norepinephrine, and it makes the hippocampus record every detail, with all the emotional nuances and associations.
Beta-Blockers and Memory Modification
As a safe way to reduce the intensity of traumatic memories, scientists have proposed using beta-adrenoreceptor blockers—the same ones that make the amygdala respond to stress. The challenge was to find a drug from this group that could cross the blood-brain barrier. Researchers settled on propranolol, widely known as a blood pressure medication. The idea is to use the drug to prevent the formation of long-term, emotionally charged traumatic memories, so it’s recommended to start taking it no later than six hours after the traumatic event. However, after 15–20 years of using propranolol to prevent PTSD, a significant body of data has accumulated, and its effectiveness is highly questionable.
Blocking Memory Formation: Protein Synthesis Inhibitors
Another interesting, though still only potential, approach comes from studying how long-term memory forms. Storing information long-term requires new neural connections or at least significant changes in the conductivity of existing ones. These processes require protein synthesis and take time—not seconds, but minutes. If you’ve ever had a concussion, you might know the feeling of losing memories from the minutes before the injury. This local amnesia happens because, at first, a memory exists only as a specific pattern of neural activity, which can easily be disrupted by a strong blow to the head. Only after several minutes does the memory “set” in the structure of neural connections. Since forming these connections requires protein synthesis, temporarily blocking it can prevent the memory from sticking.
Studies on animal models of PTSD show that if a rat receives an injection of the protein synthesis blocker anisomycin after stress, it doesn’t develop pronounced stress behavior. However, anisomycin can’t cross the blood-brain barrier on its own, so it has to be injected directly into the hippocampus—pills are out of the question. Other, safer substances like valproic acid, clonazepam, and some cannabinoids have similar, though less pronounced, effects on memory consolidation.
Reconsolidation: Editing Memories
Even more exciting possibilities come from how we recall memories. Have you ever noticed that the more often you revisit a story from your past, the more incredible details it seems to gain? That’s partly because recalling information from memory is an active process, more like reconstruction than reading. Imagination plays a big role, and the brain often forms new associative links, changing the memory. In science, this “read-rewrite” process is called reconsolidation. The biochemical mechanism is similar to the original consolidation of memory and seems to destabilize the original memory. So, when we relive the past, we could, in theory, introduce a protein synthesis blocker like anisomycin and help a patient get rid of already developed PTSD (though this has only been done in rats so far), or at least ease their symptoms. But again, this method isn’t practical for humans: protein synthesis blockers are quite toxic. However, studies show that the familiar beta-blocker propranolol, given at this moment, can reduce the emotional intensity of the memory (as can some psychological techniques, which we won’t discuss here).
New Research: Anesthetics and Memory Erasure
Fresh, promising data on this not-yet-fully-explored topic comes from a recent publication in Science Advances. Researchers used the familiar method of destabilizing a memory, but with a different drug— the anesthetic propofol. The idea came when they observed patients undergoing electroconvulsive therapy (ECT)—yes, the same “shock therapy” from “One Flew Over the Cuckoo’s Nest.” While ECT is less common today, it’s still used, for example, to treat unipolar depression.
In a simple psychological experiment, depressed patients were shown a slideshow with an emotionally charged story before ECT. Researchers found that patients who recalled the story before the next session remembered it much worse than those who didn’t. But what about anesthetics?
Today, ECT is performed under general anesthesia, without the traumatic scenes of the past. Scientists wondered: maybe the effect was caused not by the shock, but by the unnoticed anesthetic etomidate? They decided to look more closely at general anesthetics—substances that bind to the GABA receptor and enhance its activation.
This led to their latest study, which examined the effect of another similar anesthetic—propofol—on memory destabilization. They were careful not to risk patients’ lives, since propofol anesthesia can sometimes be fatal. Instead, they experimented with patients who already needed propofol for endoscopic procedures.
The experiment protocol was similar to the previous one: initial learning with an emotional story, a one-week pause, then a few questions about the story right before anesthesia in the endoscopy room. A day after the procedure, memory was tested again. The results showed that patients who recalled the story just before anesthesia remembered it much worse than those who thought about something else before getting propofol.
This confirmed that at least part of the “erasure” of destabilized memories during ECT is due to anesthesia, not the shock itself. Even more interesting, the effect of propofol only affected the emotionally charged parts of the story, barely touching the neutral ones. It’s still unclear how a substance that enhances GABA receptor activity can selectively affect memory reconsolidation, but these findings match earlier animal studies.
The Future: Selective Memory Editing
The main takeaway is that we seem to be one step closer to a technique for targeted removal of emotionally charged memories. One day, we might be able to extract traumatic memories from those who have suffered. No, uploading information into memory or completely deleting specific memories will remain the domain of Hollywood screenwriters for now, not doctors. But as we’ve seen, we can already selectively reduce the emotional intensity and detail of memories using a relatively harmless anesthetic. And that’s exactly what’s needed for effective PTSD therapy! So, let’s leave “Total Recall” vacations on Mars for later—medical memory erasure is on the horizon.
Self-control is a powerful thing, and technology is steadily increasing our “self-mastery.” Modern medicine gives us a good chance to live into our eighties, and cosmetic surgeons can help us realize our wildest fantasies. As recent headlines suggest, redesigning our own genome may be just a few decades away. But, as the saying goes, the most serious problems are always in our heads. Maybe, in time, we’ll learn to solve those too. While creating and uploading designer memories still seems far off, deleting “unwanted” memories may soon be within science’s reach. How does that make you feel—scared or intrigued?