Memory can exist without emotion

Feeling strengthens memories even in retrospect

Our memory is selective: We remember particularly emotional moments far better and more precisely than events that are of little importance to us. But even these apparently unimportant details are not completely lost, as an experiment now shows: If we shortly afterwards experience something that subsequently charges these memories with feelings or meaning, our brain digs them out again and stores them in long-term memory. This once again confirms that our memory is much more flexible than assumed for a long time.

The meaning of most memories is clear: past experiences and our stored knowledge help us to cope with our lives. This is how we learn. At the same time, however, there are countless details in everyday life that do not bring us much and that would just unnecessarily clutter our memory. As a rule, we don't remember the make and appearance of every car that passes us on the way to work, because they are not important to us. However, it is possible that these details become important in retrospect, for example because there were possible witnesses in the cars for an accident that happened to us. It would therefore be good if the brain could reanimate these seemingly forgotten memories. Whether and how this works has so far remained unclear.

In their experiment, Joseph Dunsmoor from New York University and his colleagues tested whether memories can be reawakened afterwards. To do this, they first showed their 119 test subjects 60 pictures depicting either an animal or a tool and asked them to memorize these objects. Shortly afterwards they showed them more animal and tool pictures that they hadn't seen before. This time, however, the participants received a light electric shock for one category - either the animals or the tools. As a result, the “punished” category was emotionally charged - the test subjects linked it with negative feelings. The next day, the researchers queried what they had learned - both from the images seen in shock and from those previously viewed without any emotional influence.

Memories strengthened in retrospect

The result: As expected, the test subjects remembered the category of objects better when they received an electric shock. If this was the case with the animal pictures, they recognized more animal pictures than tools. The astonishing thing, however, was that the participants now also remembered the pictures in this category better, which they had looked at long before the electric shocks without any influence whatsoever. "Obviously, the memory for neutral objects was selectively strengthened when other objects from the same category were subsequently emotionally occupied," the researchers report. These memories, which are initially unimportant, are therefore not immediately discarded by our brain, but initially stored for a short time before we finally forget them. If we then experience something that retrospectively gives these memories meaning, we can reanimate them and they are then finally saved.

"These results underscore the tremendously adaptable nature of our memory system," state Dunsmoor and his colleagues. "Our memories can not only travel back in time to bring back events from the past, they can also update old memories and give them new meaning."

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© Wissenschaft.de - Nadja Podbregar
January 21, 2015