Our day-to-day lives can be thought of as a battle on the neural level. We have tons of stimuli fighting for our attention and of those, only a few will stick. I am often surprised by which things stick in my memory for the long-term, a particular shirt I wore or a line from a song, while other seemingly more important things, like what I did when I was wearing that shirt, disappear into the recesses of my brain.
In a new study, researchers explored one important factor in the competition for our long-term memory storage – the novelty of an item or event. They found that presenting something old at the same time as something new boosted the memory for the new information.
“We were interested in how people are able to remember new things even though they are often encountered in situations where other, old things might also be present,” says Ben Hutchinson of Princeton University. “Most memory experiments present things one at a time for people to try to remember, but because we were interested in the dynamics between old and new information, we presented two things at the same time: one old thing and one new thing.”
In the study, just published in the Journal of Cognitive Neuroscience, the researchers either presented the old and new stimuli at different locations (as different parts of the brain code for different areas of space), or presented different types of images, for example, the old thing would be an image of a face and the new thing would be an image of a scene (different parts of the brain respond to these different categories of images). Using fMRI, they measured how the brain responded to the old and new stimuli and could assess how the two brain measurements related to whether or not people successfully stored the new information into memory.
The findings, they wrote, “reveal how prior experience adaptively guides learning toward new aspects of the environment.”
Hutchinson spoke with CNS about the study’s results and how it sought to more closely mirror real-world memory formation than past studies.
CNS: Why are you interested in long-term memory formation?
Hutchinson: In many ways, our memories for various life experiences make us who we are. The fact that the brain can rapidly acquire such rich and meaningful information has always been so remarkable to me that I’ve wanted to understand it as best as I possibly could. It is at the heart of what makes neuroscience so fascinating to me: the fact that an assembly of cells have evolved to be able to record and replay the vivid episodes of our lives in order to shape our current experience, sometimes profoundly so.
CNS: What is a common misconception people have about long-term memory?
Hutchinson: I think we all would like to think of memory as a passive store or vault where we can keep our unique experiences safe and unperturbed until we need them again. The truth is that long-term memories are intertwined with one another and difficult to cleanly untangle, so we frequently misremember one thing for another and sometimes create entirely false memories of which we are still very confident.
CNS: Have you seen Inside Out? If so, any thoughts on the portrayal there of long-term memory v. reality?
Hutchinson: I haven’t seen Inside Out, although I’ve talked to people who have. As I understand it, I think the movie did a good job with recognizing how being in one state of mind (happy or sad) might color our memories in certain ways, but at the same time, our memory might be better thought of as more like a tangled web than an island of marbles.
CNS: What have we known previously about factors affecting which memories get stored?
Hutchinson: There has been a great deal of work trying to understand which memories get stored and which don’t. As it stands, there are very many factors thought to relate to this in healthy humans, including the distinctiveness of what you’re trying to remember, the situation or context in which it appears, the relatedness of it to your past experiences – the list goes on. I believe one of the more influential factors is attention. That is, perhaps unsurprisingly, we tend to remember things that we are paying attention to. The difficulty as researchers is getting a sense of what, in turn, might be guiding that attention and how attention might interact with all the other factors that we also know are at play.
CNS: What was the major goal of your most recent study?
Hutchinson: The major goal of this study was to test a hypothesis about how the brain is able to learn new information when there are multiple things in the environment competing for limited processing resources. Specifically, we wanted to know if a decreased neural response to old information might effectively promote the processing of new information presented at the same time (whose neural response is not decreased). More generally, we wanted to know how our brain is able to effectively use our past experience to guide learning about new things in the environment.
CNS: What were your most excited or surprised to find and why?
Hutchinson: Although we went into this study with a specific hypothesis in place, we were still very (pleasantly!) surprised and excited to find that our hypothesis was supported by the data. In many ways, the results could have easily gone the other way, as there are many situations where your processing is biased towards old information (the opposite of what we found), which would have still been interesting, although not what we hypothesized.
CNS: How does this work fit in with past work on long-term memory?
Hutchinson: Much past work on long-term memory formation has found that when there is greater activity in the brain regions that code for something, you are more likely to remember that thing later on. Here, we hopefully extend this past work by articulating how memory for something is not only related to the activity it evokes in the brain, but also by how other things in the environment are processed in parallel.
CNS: What do you most want people to understand about this work?
Hutchinson: A big takeaway from this is that long-term memory formation does not occur in a vacuum. That is, in real life, we don’t encounter things one at a time in isolation, the way things are typically done in item memory experiments (including my own past work!). Rather, throughout our lives, our world comes to us as a large, constant flood of information and our brains must decide what is worth focusing on and perhaps remembering later. Here, we wanted to highlight how single items in this flood of information might stand out not only because they are eye-catching or important, but simply because they haven’t been encountered before.
CNS: What’s next for this line of work?
Hutchinson: In this study we looked at one very basic neural marker of a past experience: lower evoked activity upon repetition of an item in regions which code for that item. However, memory refers to the multiple ways in which our past can influence our present and there are many neural and behavioral markers that have not been explored in the same way as was done here. We are very interested in exploring how other neural and behavioral markers of memory might bias the competition between old and new information in order to guide learning and behavior.
-Lisa M.P. Munoz
