Did That Just Happen? How Your Brain Alters Mental Timelines

Memories Brain People Activity

It sounds like a scene from a detective novel: The witness sees a body falling from the window, and then hears a loud noise that sounds like the body hitting the ground. But what if the noise actually came before the fall?

Navigating through our memories of past events seems to be easy task, but we don't always get it right. We might remember things that didn't happen, and we can also get the time wrong. We may remember incidents as happening closer together or farther apart than they actually did, or even completely mess up the order of events.

Exactly how the brain organizes memories in relation to each other in time has long puzzled scientists. In a new study, researchers set out to identify the nature of brain activity that puts a time stamp on our memories.

"Our memories are known to be 'altered' versions of reality, and how time is altered has not been well understood," said study researcher Lila Davachi, an associate professor of Psychology at New York University.

"People think their memories are a reflection of reality. They somewhat are, but they are a better reflection of what's happening inside their head," Davachi told Live Science. [10 Things You Didn't Know About the Brain]

The new research shows a link between activity patterns in the hippocampus — a region known to be involved in forming memories — and how near or far away in time people placed their memories, according to the findings detailed Wednesday (Mar. 5) in the journal Neuron.  

Did all that happen at one party?

To understand how people remember the order in which events occurred, the researchers had 21 study participants watch images of faces flash a few seconds apart, with an image of an outdoor scene flashing in between the faces. The idea was that the faces each represented an event, for example meeting a new person, and the scene represented where that event took place, for example in a party.

"We were trying to create stability in the environment, trying to mimic what it feels like when you go into a room or to a party and stay there for a long time," Davachi said. "The basic spatial context is the same, but you're seeing lots of different people."

Meanwhile, researchers used a brain-imaging technique, fMRI, to scan participants' brain activity in the hippocampus ( via livescience.com ).

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