We tend to forget the bad and stay with the good. In extreme cases, there are people who erase traumatic memories from their head. There is no trace of them. Scientists proved decades ago that the phenomenon is common among individuals of all cultures and latitudes, but the brain physiological mechanisms involved were unknown.
Until now. A recent work by researchers at the University of Texas at Austin (UT) published in the Journal of Neuroscience provides clues to understand the origins of this psychological defensive barrier. And it has been a surprise: the brain has a harder time forgetting an unpleasant experience than fixing it.
The scanner does not lie
The researchers used neuroimaging techniques to record patterns of brain activity. They taught a group of healthy adults images of faces and scenes, and asked them to make an effort to remember or forget those that were pointed out to them.
Instead of analyzing what happened in the brain areas involved in the control of information and long-term memory-the prefrontal cortex and the hippocampus-they focused on the regions linked to perception, especially the visual cortex, and in the patterns of activity that correspond to the representations made by the memory of complex visual stimuli.
They observed that, as was suspected, people have some capacity to decide what we forget, and that starting it requires moderate brain activity in areas related to the senses and perception, greater than what is required to fix a memory. According to Tracy Wang, psychologist and principal author of the study, "is the intention to forget what increases brain activity, and when it reaches a certain threshold, we begin to forget that experience that affects us."
The researchers also found that study subjects tended to forget scenes more than faces; The latter usually provide us with much more emotional information, which confirms that feelings play a decisive role in the memory mechanisms of human beings.
A flexible capacity
This work affects something known: memory is dynamic. The brain builds from the experiences and sensations a memory that does not remain frozen: the neural circuits modify it in the light of new experiences, or eliminate it, in processes that usually take place when we sleep.
Jarrod Lewis-Peacock, one of the authors of the study, said on the UT website that "now that we have discovered indications of how the brain works to weaken certain memories, we can use this knowledge to develop treatments that help people get rid of of memories that do them a lot of psychological damage, so much so that they can make them sick ".