We often recall memories in our everyday life, and yet our memory could be playing tricks on us. According to recent results, the same zone of the brain is activated, regardless of whether the memory being recalled is right or wrong. What is even more surprising is that our memory travels through time in its own way.

Donna J. Bridge, a neuroscientist at the Northwestern University, carried out a study on how our memory can be consolidated or even changed. Seventeen subjects were asked to memorize the location of dozens of objects that were briefly shown to them on a standard computer screen.
First, they had to find the original locations, using their computer mouse to drag the objects from the center to the position they believed to be the initial position of each object. None of the volunteers managed to find the correct locations. The distance between the two points was measured to be used later on in the study.

Then, they had to find the original position of the objects among three choices: the original location, the incorrect answer that they had given, and a position between the two. In this case, 16 out of 17 people placed the objects in the same place as before i.e., in the wrong place. This suggests that the participants created an incorrect memory when they carried out the first part of the test.

In the third situation, the subjects were asked to move the object to a random location but at the same incorrect distance as the one measured previously. The participants were not told that this location was wrong. Then, they had to move the object again from the center to the location they thought to be right i.e., where they saw the object appear originally. The results proved to be surprisingly good. Finally, the results were as good in a last situation when they were given three choices.

While the subjects were taking part in these tests, their brain activity was measured, showing that it was the same zone of the hippocampus that was activated in both cases: “correct” memory or “incorrect” memory. Donna Bridge concluded that “regardless of what is important to you now, the hippocampus is responsible for keeping a representation stable or changing it”.

The results of this study explain why we find it hard to recognize somebody on an old photo. In fact, researchers say that our memory rewrites our past based on our present experiences. The authors also add that the first role of memory is to help us to make the correct decision at a given time. This is why it has to remain up-to-date. What is relevant today can replace what was relevant yesterday.

This knowledge could have some impact in certain areas, in particular during court cases where many people base their accounts on their memory.