When memories are remembered, they are very often associated with emotions. This is the case for example of your first day at school or your wedding. But in the event that feelings are less positive, researchers have found a way to remove them from your memory.
For some time now, scientists have known that emotional associations, or valences, are malleable. Therapists often use this property of memory to treat patients with post-traumatic stress, among others. However, the nervous mechanisms that trigger these memory / emotion combinations have long remained mysterious. Today, a study by the Massachusetts Institute of Technology reveals what are the most active neurological circuits in this association between memory and emotions. In addition, neurologists have demonstrated that they can cancel the valence of a memory by activating certain brain cells.
Two regions of the brain are known to be crucial in the formation of new memories: the hippocampus and amygdala. The hippocampus deals with the appearance of memories, their organization and their classification. The amygdala is involved in the emotional treatment of these. Yet, until now, researchers did not know where in the neural circuit valencies were bound to memories. So they used a technique called optogenetics to manipulate the activity of neurons. With the aid of a photosensitive protein, they identified the useful cells, both in the hippocampus and amygdala. These neurons are actually those that are activated when they have experienced a rewarding experience or that we feel the fear.
The team then placed mice in a two-piece area and observed where they preferred. Then they lit a blue light to stimulate the neurons of the mice to make them feel fear each time they entered their favorite area. They quickly avoided this place to go to the other, which suggests that the memory of fear was present in them. The same experiment was conducted with the feeling of gratitude to rodents, activating this feeling when they went to the room they liked least in theory. Logically, the mice began to go there more frequently, demonstrating that they remembered this pleasant feeling.
Later, scientists tried to remove the valence of a memory by putting the mice in the opposite situation. When they placed these animals in the two-piece box, those who were basically fear-conditioned and avoided the room in question again began to prefer this place, suggesting that the valence was reversed. This also worked for the mice that had been rewarded, and therefore subject to fear afterwards. This whole study highlights the fact that valences are encoded in a circuit that connects the dentate gyrus (part of the hippocampus) with the amygdala. Researchers are currently working on a solution that could effectively cure depression.
We are delighted to learn that a technique to suppress negative emotions is emerging. We congratulate the researchers who discovered this method. Hopefully in the near future this will lead to effective treatments for phobias, depression or post-traumatic stress. However, some of the editors would be very worried about being influenced in this way. Would you let doctors manipulate your brain to remove your most terrible memories?