The changeable ‘brand’ of memory

In our barest state, we are alone, save for our memories. It is our stirrings from within that make us more than our bodies. It is also what makes us distinct from each other even if live through same fundamental template consisting of birth, falling in love (or some form of it), working on something, getting old and then dying. 

The circumstance of your birth may have been funny or tragic, the place where you lived when you were 5 may have been the happiest place on earth or simply hellish; a broom may have unleashed your cleaning prowess or a weapon that seemed to have sworn to constantly target your behind. A place, object, event or even a song brushed against your existence and left a trace in your mind that is very different from how someone else would remember them. In sum, every memory inhabits a different emotional context. But what if you could change the emotional charge of those memories?

Scientists have known for a while now that memories do not just reside in one part of the brain. The hippocampus is known to serve as the main harbor for long-term memories but the other things that define that memory seem to depend on the connections of the hippocampus with other parts of the brain. The emotional charge of those memories come from another part called the amygdala, a brain part in the middle “emotional” part of the brain that looks like a tiny bluetooth earpiece. The scientists thought that the trick of changing the emotional charge of a memory lay in figuring out the switching in the connections between the amygdala and the hippocampus.

They experimented with two groups of male mice. To one group of mice, they delivered electric shocks to their feet. To another group, they gave them some “romantic” time with female mice. Given those two distinct experiences, the scientists identified which neurons were activated in those experiences and genetically modified those neurons to respond to blue light. Then later, the scientists shone blue light to all the male mice from the two groups when they were neither being shocked nor busy with female mice. The result was that the electrically shocked mice fled while the other set, stayed.

Changing the emotional mark of an experience

The scientists wanted to test if they could change the emotional charge of the electrical shock and the “romantic” time with the female mice. So for the next round, they gave the opposite experience to each group while exposing the mice to blue light. And whola! The previously shocked mice did not run away anymore from the blue light but the previously “lucky” male mice did!  Blue light no longer meant the same for the two groups of mice and they acted accordingly.

This study was published in the journal Nature, proving, at least for mice which has a brain structure similar to ours, that the “meaning” of a memory could be changed. The scientists think that the neurons of the hippocampus are being rerouted to the neurons that are now giving it a new emotional charge.

Is it wise to change the emotional mark of memories?

It is easy to see this finding contributing to therapies for severely traumatized patients, including pets who have been abused. Those who have been through the harrowing experience of war, abuse or disaster could certainly benefit from something that “transforms” the baggage so that they have a better chance of dealing with the rest of their lives.

But there are two things that I wonder about. One is, what happens to the neurons that retain the lesson of having been through a “bad” experience so that you don’t do it again? The scientists said they are just there but under what conditions do they kick in again?

Another is, that it is not yet clear how this could work when it comes to memories that could not simply be labeled “positive” or “negative.” Most of our memories are just too complex to be labeled as such and these have come to define our very personalities. “San Francisco” to me, for instance, means emotional ‘disaster” and ‘redemption” at the same time. “Smile”, the song, is both sweet and bitter to me, identified with loved ones who have long passed. When we mess with the simple “positive” and “negative” memories, aren’t they linked with other more complex memories that we would never want to be eroded?

“Bookends” is a short poignant song by Simon and Garfunkel that stops with: “Preserve your memories. They’re all that’s left you.”

What are the things you wished meant something else in your life? – Rappler.com

Maria Isabel Garcia is a science writer. She has written two books, Science Solitaire and Twenty One Grams of Spirit and Seven Ounces of Desire. Her column appears every Friday and you can reach her at sciencesolitaire@gmail.com.