A team of scientists has discovered a group of cells in the brain which suppress fearful memories when activated, and vice versa.
According to Michael Drew, associate professor of neuroscience and senior author of the study, "There is frequently a relapse of the original fear, but we knew very little about the mechanisms. These kinds of studies can help us understand the potential cause of disorders, like anxiety and PTSD, and they can also help us understand potential treatments." Researchers found that the fear-suppressing brain cells hide in the hippocampus, as opposed to the traditional belief that associates fear with the amygdala. The hippocampus which serves various functions regarding memory shaping and storage, supposedly also tethers fearful memories to the place where they took place. Prof. Drew said, "Our paper demonstrates that the hippocampus generates memory traces of both fear and extinction, and competition between these hippocampal traces determines whether fear is expressed or suppressed."
Researchers placed mice in a box and induced fear through a harmless shock. Following that, whenever the mice were in the box they would display fear. However once the extinction memories formed following repeated exposure to the box without a shock, the mice were no longer fearful. The safe memories are called "extinction memories”. “Artificially suppressing these so-called extinction neurons causes fear to relapse, whereas stimulating them prevents fear relapse," Drew said. "These experiments reveal potential avenues for suppressing maladaptive fear and preventing relapse." The findings could be useful in the treatment of anxiety, phobias and post-traumatic stress disorder (PTSD).
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