Old or New Memories Can Bias Future ActionsCan old memories change the way we think? Do new experiences cement recollections?

A new study shows that remembering something old or noticing something new can bias how you process subsequent information.

In the study, reported by New York University researchers in the journal Science, researchers discovered that our memory system can adaptively bias its processing towards forming new memories or retrieving old ones based on recent experiences.

For example, when you walk into a restaurant or for the first time, your memory system can both encode the details of this new environment as well as allow you to remember a similar one where you recently dined with a friend.

The results of this study suggest that what you did right before walking into the restaurant can determine which process is more likely to occur.

Prior studies have shown that both encoding new memories and retrieving old ones depend on the same specific brain region — the hippocampus.

These findings have been challenged as experts wondered how the same part of the brain could perform two tasks that are at odds with each other?

The issue boils down to a distinction between encoding, or forming a new memory, and memory retrieval, or recalling old information.

Specifically, encoding is thought to rely on pattern separation, a process that makes overlapping, or similar, representations more distinct, whereas retrieval is thought to depend on pattern completion, a process that increases overlap by reactivating related memory traces.

An experiment was devised to help straighten out the neurological paradox – that the hippocampus can be biased towards either pattern completion or pattern separation, depending on the current context?

In the study, participants rapidly switched between encoding novel objects and retrieving recently presented ones.

The researchers hypothesized that processing the novel objects would bias participants’ memory systems towards pattern separation while processing the old ones would evoke pattern completion biases.

In the experiment, researchers found that participants’ ability to notice the new details and correctly label those stimuli as “similar” depended on what they did on the previous trial.

Specifically, if they encountered a new stimulus on the preceding trial, participants were more likely to notice the similar trials were similar, but not old, items.

By contrast, in another experiment, the researchers demonstrated that the same manipulation can also influence how we form new memories.

“We’ve all had the experience of seeing an unexpected familiar face as we walk down the street and much work has been done to understand how it is that we can come to recognize these unexpected events,” said Dr. Lila Davachi, an associate professor in NYU’s Department of Psychology and the study’s senior author.

“However, what has never been appreciated is that simply seeing that face can have a substantial impact on your future state of mind and can allow you, for example, to notice the new café that just opened on the corner or the new flowers in the garden down the street.”

“We spend most of our time surrounded by familiar people, places, and objects, each of which has the potential to cue memories,” added doctoral student Katherine Duncan, the study’s first author.

“So why does the same building sometimes trigger nostalgic reflection but other times can be passed without notice? Our findings suggest that one factor maybe whether your memory system has recently retrieved other, even unrelated, memories or if it was engaged in laying down new ones.”

Source: New York University