Swiss researchers studied the neurobiological basis “rewriting” fearful memories in mice. Scientists have found that behavioral therapy targets the neural network, in which the “recorded” fear, they formed a new, safe memories, and the horror experienced by earlier passes, they say in Science.
From a kind of fear at some point in their lives suffers more than a third of all people. Phobias strike more often urban residents and women, and posttraumatic stress disorder (PTSD) annually registers more than 1% of the world’s population — those who survived the war, terrorist attacks, disasters and accidents, acute social event. Sometimes it can become even the death of a loved one.
At the moment the only effective method of treatment of psychopathological conditions like behavioral therapy, when a person in a controlled environment is exposed to trigger his fear, but without pain or traumatic effects, and over time, the fear passes. However, the mechanisms of the success of this treatment approach is unclear, and to date not fully understood how the therapy works on the neurobiological level.
The latest technological advances of neurobiology for allow you to quite effectively manipulate the activity of individual nerve cells and record their activity with a precision of few neurons to understand how to form certain neuronal networks — for this the scientists used methods chemogenetic and optogenetics. These methods have used a group of researchers led by Johan Graff (Johannes Gräff) from the Federal Polytechnic school of Lausanne, to follow the formation of fear in mice, and then try to get rid of methods, reminiscent of behavioral therapy, while carefully watching the activity of neurons.
Scientists discovered that the weakening of the old fear in the brain associated with activity of the same group of neurons that are involved in storing these memories, and they are in the dentate gyrus of the hippocampus. The authors worked with mice that have the genes of the neurons in this brain region was expressed fluorescent protein acting as a indicator of neuronal activity. Placing the animals in the box where their legs beat light discharge current, the scientists gave the animal a conditioned reflex of fear and have identified a subpopulation of neurons in the dentate gyrus, where this fear is “enrolled”. Even after a month after the experiment, the mouse was in the box, showed a fear response, and the corresponding engram in this moment was active.
Then wean to fear by placing in the same box, but not affecting the current. Later, when researchers checked the brain of rodents, they found that the mice were no longer afraid at the level of behavior, but the same engram, who previously was responsible for the terrible memory was still active, but now do not entail the corresponding behavioral manifestations.
Scientists tested observable fact, optogenetics methods of disabling cells of neural ensemble of fear in some animals, and found that such mice are much worse trained not to be afraid of, compared to the control group. In this case, if the same network of neurons in the dentate gyrus optogenetics activated, the animals ceased to fear faster.
Thus, the authors came to the conclusion that the weakening of the old horror depends on the activity of neurons, which over the memories of this fear the answer. And behavioral therapy helps to overwrite the value of an engram without any negative reactions.
By the way, not so long ago we talked about how memories are formed, and in another study the researchers found outthat mice also are able to understand what they remember and what is forgotten.