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EarthSky // Human World, Science Wire Release Date: Feb 05, 2014

How your memory rewrites your past

Your memory isn’t like a video camera. Instead, your memory plucks fragments of the present and inserts them into the past to create a story to fit your current world.

Image credit: Hartwig HKD/Flickr

Image credit: Hartwig HKD/Flickr

Your memory rewrites the past with current information, updating your recollections with new experiences, say Northwestern University researchers. Love at first sight, for example, is more likely a trick of your memory than a Hollywood-worthy moment.

The study appears in the February 5 issue of the Journal of Neuroscience. Donna Jo Bridge, a postdoctoral fellow in medical social sciences at Northwestern University Feinberg School of Medicine is the lead author. Bridge said:

When you think back to when you met your current partner, you may recall this feeling of love and euphoria. But you may be projecting your current feelings back to the original encounter with this person..

The study looks at how memory is faulty, and how it can insert things from the present into memories of the past when those memories are retrieved.

To help us survive, Bridge said, our memories adapt to an ever-changing environment and help us deal with what’s important now. She said:

Our memory is not like a video camera. Your memory reframes and edits events to create a story to fit your current world. It’s built to be current.

All that editing happens in the brain’s hippocampus, the new study found. The hippocampus, in this function, is the memory’s equivalent of a film editor and special effects team.

For the experiment, 17 men and women studied object locations on a computer screen with varied backgrounds – such as an underwater ocean scene or an aerial view of Midwest farmland. Next, researchers asked participants to try to place the object in the original location but on a new background screen. Participants would always place the objects in an incorrect location. For the final part of the study, participants were shown the object in three locations on the original screen and asked to choose the correct location. Their choices were: the location they originally saw the object, the location they placed it in part 2 or a brand new location. People always chose the location they picked in part 2. Bridge said:

This shows their original memory of the location has changed to reflect the location they recalled on the new background screen. Their memory has updated the information by inserting the new information into the old memory.

Participants took the test in an MRI scanner so scientists could observe their brain activity. Scientists also tracked participants’ eye movements, which sometimes were more revealing about the content of their memories.

The notion of a perfect memory is a myth, said Joel Voss, senior author of the paper and an assistant professor of medical social sciences and of neurology at Feinberg. Voss said:

Everyone likes to think of memory as this thing that lets us vividly remember our childhoods or what we did last week. But memory is designed to help us make good decisions in the moment and, therefore, memory has to stay up-to-date. The information that is relevant right now can overwrite what was there to begin with.

Read more from Northwestern University