It’s pretty general knowledge that nearly anyone with a history of abuse, neglect or damage in some type of way knows what it’s like to at times, unexpectedly relive memories you would’ve otherwise preferred to forget, and despite your protestations, it feels like you’re right back in the moment that caused you so much grief to begin with. All it takes is a familiar smell, a taste of your past, or a common familiarity that you may have come across in the moment. But whether the memory that re-surfaces is positive or negative, the emotional impact (and sometimes, burden) that it has on you is clear and unforgettable. But, what’s actually happening in your brain when it relives old memories unexpectedly?
Catherine Loveday, a principal lecturer in cognitive neuroscience at the University of Westminster told Motherboard that building and revisiting memories is akin to walking through a thick brush. “If you imagine walking through a really high, grassy field, and the first time you walk through, you’re really having to bash through the yard,” she explained. “The person walking behind you can get through a little bit more easily.”
“When an association has only happened once, you won’t have a very strong reaction, so that trigger won’t easily set up the whole memory,” Loveday continued. However, “if that association continues time and time again, it won’t take any effort at all for one thing to trigger another.” and while the idea of triggering can also be applied to good memories, the bad ones always feel more ingrained.
“Evolution-wise, it’s very important to survive. If people treat you badly, you remember it for the rest of your life. It was one of the key evolutionary functions to keep us alive,” said Ming Zhou, a professor at University of Toronto’s Department of Physiology and a Michael Smith Chair in Neuroscience and Mental Health. “We remember who is not good to [us]. That’s how you survive. Those people who are good to you, who don’t bother your survival, you tend to not remember them,” Zhou explained.
According to Zhou, the best information we have about how our brain store and recalls memory is from studying LTP, aka long-term potentiation. So, what exactly is LTP? LTP is the mechanism largely used for learning memory. “You read a book, you go to university—all that knowledge is part of learning memory,” Zhou said. In other words, LTP causes long-term strengthening of synapses between neurons—and stronger pathways means stronger memories, which can ultimately be for better or for worse.
“In the case of physical injury, emotional injury, all these could trigger our LTP,” Zhou said. “That is why we see people having long-term fears, long-lasting anxiety.” And memories rooted in emotions are always going to feel stronger. Remember Loveday’s idea of hacking your way through a grassy knoll for the first time? “The more emotional [the memory] is, the quicker and easier those associations are made,” she explained. “You don’t need to make so many runs through the grass.”
“I think the only way to really get rid of them is to make new associations,” Loveday said. “If you can broaden that trigger out, it’s more likely to kill the other one.” Loveday suggests identifying what is really causing the memory – it could be as simple as a particular smell, a particular location, or even a song.
Additionally, Loveday has expressed that It’s hard to say exactly if a trigger warning actually would makes a difference or not. However, at this point, the brain is too complex and currently too unknown to make any definitive claim about what exactly will or won’t trigger something in your own brain.