February 5, 2014
Brain Edits, Splices Past Memories With Current Events
[ Watch the Video: Brains Edits Past Memories ]
Brett Smith for redOrbit.com - Your Universe Online
While we may like to think of our brains as a video camera that records events exactly as they happen, a new study from scientists at Northwestern University has found that the brain acts more like an editing studio, cutting and splicing past events based on present circumstances.
"When you think back to when you met your current partner, you may recall this feeling of love and euphoria," said Donna Jo Bridge, a postdoctoral fellow in medical social sciences at Northwestern University and lead author of the new study, set to be published this week in the Journal of Neuroscience.
"But you may be projecting your current feelings back to the original encounter with this person,” Bridge added.
The study team found that editing happens in the hippocampus, which reframes and edits events to create a narrative that fits an observer’s current world view.
For the study, 17 men and women studied nearly 170 object locations on a computer screen with diverse backdrops such as an underwater scene or an aerial view of farmland. Next, scientists asked volunteers to try to place the object in the original location but on a new backdrop. Study researchers found that their volunteers would always place the objects in a wrong location on the screen.
For the last part of the study, volunteers were shown the item in three locations on the original backdrop and asked to select the correct location. Their options were: the location they originally saw the item, the location they placed it in part two of the experiment or a completely new location.
"People always chose the location they picked in part two," 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."
Study volunteers performed the test in an MRI scanner so researchers could observe their brain activity. The study team also tracked participants' eye motions, which at times were more revealing about their memories – and if there had been conflict in their selections – than the location they wound up choosing.
Study author Joel Voss, an assistant professor of medical social sciences and of neurology at Northwestern, said the idea of a perfect memory is a myth.
"Everyone likes to think of memory as this thing that lets us vividly remember our childhoods or what we did last week," Voss said. "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."
Bridge noted the study could have consequences for analyzing testimony in a court of law.
"Our memory is built to change, not regurgitate facts, so we are not very reliable witnesses," she said.
Bridge did note that the study was conducted in a controlled experimental setting.
"Although this occurred in a laboratory setting, it's reasonable to think the memory behaves like this in the real world," Bridge said.