Old memories are forgotten for new memories

For new memories, old ones are simply forgotten

03/17/2015

Human memory can be rigorous in sorting the past. The brain suppresses competing memories: new ones have to make way for new ones. Remembering also triggers forgetting at the same time.

Brain suppresses competing memories
Even if it sounds absurd at first, scientists have shown in an experiment that remembering also makes us forget. As the news agency dpa reports, it showed that when people remembered something concrete, they forgot similar, in the context disturbing memories. The British researchers report in the journal „Nature Neuroscience“, that the brain actively suppresses the competing memories. So, the process of remembering helps shape which aspects of our past are accessible - and which are not.

Extinction of memory
As the scientists around Maria Wimber of the University of Birmingham write, remembering seems to be a double-edged sword. Although older studies have shown that repeated memory stabilizes the memory content, there has also been evidence that remembering also triggers forgetting. Experts believe that there is probably an inhibitory control mechanism that is responsible for this: This suppresses memories that „butt in“, if you want to remember something specific. This suppression then gradually led to the extinction of memory. However, so far no one has been able to show in the brain how this inhibition mechanism works.

Link keywords to images
To change this, the researchers scanned the brains of their subjects with functional magnetic resonance imaging (fMRI). With it, active brain areas can be visualized, so that one can watch the brain virtually at work. First, the study participants learned to associate certain keywords with two different images, such as the word „sand“ with a picture of Marylin Monroe and a picture of a hat. Then the subjects should remember the keyword to the first associated image that they had learned. The researchers assumed that the second image would intervene as a disruptive factor. The participants then each indicated whether they remembered a face or an object. Because the two categories delivered a different signal in the scanner, the scientists were able to determine whether the subjects had called the correct image.

Around three quarters remember the right picture
In 74 percent of the experiments, the subjects remembered the data according to the correct (the first) image. It is also reported that they often remember the second picture in the case of errors rather than a control picture. In the course of the experiments, however, this happened less and less often. As the scientists explain, this suggests that there is an inhibitory mechanism that gradually suppressed the disturbing memories. The researchers also showed in further experiments that the brain activity associated with the second image decreased during the course of the repetitions. Thus, the study participants forgot the second picture the more completely, the stronger the decrease was. Furthermore, there is a connection between the activity in the prefrontal cortex of the brain and the erasure of memory, as the scientists showed. The stronger the activity, the greater the decrease of the fiery fire and the more forgetting. Already in earlier works, this region had been associated with the erasure of memories.

Forgetting can be helpful
„People usually believe that forgetting is something passive. Our research shows that instead they themselves are involved in what they remember from their lives“, explains study leader Michael Anderson of the MRC Cognition and Brain Science Unit in Cambridge, UK. „The idea that the very act of remembering causes forgetting is surprising and can tell us more about selective memory and about self-delusion.“ Maria Wimber adds: „Forgetting is often considered negative, but of course it can be incredibly helpful if you try to forget a negative memory.“ These include traumatic experiences, such as experiencing violence or sexual abuse. „So there is an opportunity to apply this knowledge to help people“, so Wimber. (Ad)