http://web.mit.edu/newsoffice/2013/how-old-memories-fade-away-0918.html

I found this article on memory extinction simultaneously fascinating and troubling, both on an individual level and a social one. I encourage you to read it.

We all have memories that we would like to forget in some way—the growing pains of adolescence, the moments of embarrassment and inexperience, the tragedies of losing loved ones—but, for some reason, they stick with us and continue to affect our lives. In a recent MIT study, scientists say that they have discovered a gene involved in ‘memory extinction’, the process by which the brain replaces older memories with new experiences.  The term ‘extinction’ refers to conditioned responses that fade away as older memories are replaced by newer ones.

The article cites that “enhancing the activity of this gene, known as Tet1, might benefit people with post-traumatic stress disorder (PTSD) by making it easier to replace fearful memories with more positive associations.” This leads to the inevitable question: if you could forget specific memories, would you? And if you can forget, are you doomed to repeat the actions of the past at some point in the future?

The research team experimented on two groups of mice: one with normal levels of the Tet1 gene and one with the gene “knocked out”, essentially removed from brain activity. Both groups of mice were conditioned to have negative associations with a certain cage; the researchers did this through electric shocks. The mice were later placed in that same cage but received no shocks, which allowed them to possibly adjust their previous, negative associations with the environment. Over time, the mice with normal levels of the Tet1 gene were able to lose their negative associations with the cage, meaning their new experience was able to override their memory of the electric shocks. Meanwhile, the mice without the Tet1 gene remained fearful of the cage (even when it didn’t shock them), meaning the new experience was not able to extinguish previous memory.

Therefore, the mice without the gene were able to form new memories and learn new tasks, while the mice deficient in the gene were not able to forget their previous associations and memories. The article points out that “memory extinction is not erasure of the original memory. The old trace of memory is telling the mice that this place is dangerous. But the new memory informs the mice that this place is actually safe. There are two choices of memory that are competing with each other.” The mice without the Tet1 gene are getting stuck in processing new information and, as a result, must rely on old memory even as it becomes outdated.

The team behind this experiment is now looking at ways to increase Tet1 gene levels artificially and studying its effects on extinction and memory processes in general.

This study caught my attention not only for its subject—doesn’t ‘memory extinction’ sound like a covert operation in a sci-fi movie?—but also the notion that new experiences can override memories of the past. I understand how enhanced levels of the Tet1 gene could help people suffering from PTSD function better in the world, but why stop there, why not include anybody who wishes to forget certain memories of the past. (After reading this article, I am encouraged to revisit the movie Eternal Sunshine of the Spotless Mind, which seems more prescient now more than ever).

This reading inspired me to think about my own memory. For example, I am able to remember an infinity of images—people, places, things. Some important, others less so. One memory conjures up another, but at the same time, excludes other possibilities to resurface. To remember is to follow a particular string of memories, one that has codified over time; you follow a set of directions leading back home, choosing one series of streets over another. It seems to me that part of remembering is forgetting as well. Recalling your specific memory seals you off from recognizing other perspectives of the past. Perhaps, in the end, it is our forgetting as opposed to our recollection that identifies us and makes us human.

I will admit there are types of memories that can cripple people and prevent them from moving on from the past. Memories of physical violence, psychological abuse, torture and warfare come to mind. These memories are perhaps worth exploring from the vantage point of extinction; however, on the other hand, there are experiences we never wish to forget. We strive to preserve valuable information so that it remains pure and untouched by time. These memories undergo a process called memory consolidation. Certain memories become consolidated through enough repetition or retrieval that they start to feel like second nature, and the task of forgetting consolidated memories can sometimes prove impossible.

A memory, a glance, a touch, an image, a feeling, a name, a minuscule detail—any of these parts of life can somehow reach consolidation, even if something else inside tries to resist or even forget. To retrieve consolidated memories involves the process of either recall or recognition; yet, a memory can exist even without the brain recalling it. A memory can survive for decades without being remembered; it can still reassert itself when another memory resurrects it from a deep layer of the network. And when that memory rises to the surface, the recalled experience can be as electrifying as that original moment of association.

It must be true that we are what we remember. The more we recall a certain memory, the more pathways are linked to it: seminal moments in a lifetime such as the birth of a child, the death of a loved one, or a wedding day are continuously recalled and therefore become the most accessible to us. In this way, these memories grow durable over time. The innocent scenes of childhood, the awkwardness of puberty, the traumatic tragedies of life are recalled over and over again, and so by the time we reach old age, these memories are nearly indestructible. Sometimes, it is not death that I fear, but the loss of memory. For what is the self with no memory of the past?

This idea of memory extinction raises some important ethical questions as well. What would happen if part of society could forget past experiences? If we can’t remember, then are we forced to repeat past events in some way in the future? So many events in our culture—September 11^th, the Economic Recession, the Boston Bombing—are tagged with the phrase, “Never Forget,” as a way to preserve them and prepare ourselves in case they reappear in the future. So, is it all right to forget some events and not others, or is it immoral to purge only the pain and injury of the past?

If you could forget, would you? I think most people would initially be intrigued by the possibility, but in the end, it’s our memory—the entire spectrum of memories—that forms the core of our identity. Removing one part of the past, however painful it may be, would be to eliminate a characteristic, or personality trait, or even some wisdom that was only gained through trauma. Whatever happened to us in the past, isn’t it all part of us in the present as well as the future?

I point this to you: would you choose to live in a society where people had the power to forget or extinguish the memories they didn’t like? What would that mean for individual memory and social, collective memory as a whole? Would it mean living in a society that remembers only those things we want to remember? Would we be better for it or just more ignorant? And, what are the moral implications of memory extinction? I know that this study was only performed on mice, but the possibilities for humans seem endless.