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remember and forget

Traumatic memories are persistent. They keep coming back even years after the event that caused them, and do not respond to attempts to exterminate them. Most people manage, with the help of hard work, to take control of the memories, and push them into the back drawers of their minds. But in others, the repeated flooding of difficult memories causes the development of post-traumatic syndrome.

From the right: Uri Livna, Oded Kluyer and Dr. Roni Paz. Full support. Photo: Weizman Institute
From the right: Uri Livna, Oded Kluyer and Dr. Roni Paz. Full reinforcement. Photo: Weizmann Institute

Traumatic memories are persistent. They keep coming back even years after the event that caused them, and do not respond to attempts to exterminate them. Most people manage, with the help of hard work, to take control of the memories, and push them into the back drawers of their minds. But in others, the repeated flooding of difficult memories causes the development of post-traumatic syndrome. A series of studies by Dr. Roni Paz and the members of his group, from the Department of Neurobiology at the Weizmann Institute of Science, reveals the brain mechanism responsible for the durability of memories, and even suggests a way to reduce the durability, and help the memory to be forgotten.

To create the "traumatic memories" the scientists used a standard learning process, in which a neutral stimulus (in this case - a certain sound) is accompanied by negative reinforcement (a bad smell). The challenge facing the research team, led by research student Uri Livna, was to create two identical traumatic memories, one of which tends to be quickly forgotten, while the other is resistant to extinction. To this end, they used a paradigm from the field of cognitive psychology - used, for example, in child education and animal training: learning in which each stimulus is accompanied by reinforcement ("full reinforcement learning") is retained for a shorter time than learning in which reinforcements are received partially and randomly ("partial reinforcement learning" or " probabilistic learning"). Although both processes lead to the same intensity of learning, and to the same behavioral response, "probabilistic learning" is more difficult to eradicate. While learning, the researchers used electrodes to monitor the electrical activity of two areas of the brain: the amygdala, that in previous studies by Dr. Paz and of other scientists it was discovered that it is involved in memories of an emotional nature, and an area in the frontal cortex, called ACC, whose activity is known to be abnormal in those suffering from post-traumatic syndrome. The ACC is related to learning under reinforcement conditions, and to the creation of a world picture built from complex and statistical patterns. For this reason, the researchers suspected that he might be involved in partial probabilistic learning.

The research findings, published in the journal Neuron, Confirm the suspicions. It turns out that, in contrast to full reinforcement learning, which is carried out exclusively by the amygdala, partially probabilistically reinforced learning is done during a coordinated dialogue between the amygdala and the ACC, and that the coordinated activity level of the two areas predicts the durability of the memories . The findings may explain, for example, the following statistic: soldiers who were transferred from their permanent unit during wartime - and as a result were exposed to an unfamiliar and unexpected environment - are more likely to develop post-traumatic syndrome. "However, our findings not only explain why some people develop post-traumatic syndrome while other people do not," explains Dr. Paz, "but show that one person may develop the syndrome following a certain event, but not following another event. The source of the difference is not only genetic, as is commonly thought, but depends on the exact way in which the memories were created."

Based on these findings, the scientists wanted to try to see if they were able to disrupt the storage mechanism of the traumatic memories, thus reducing their durability. To this end, the research team, led by Dr. Oded Kluyer and research student Rotem Ganud, used a technique of intracerebral electrical stimulation using an electrode - which is currently accepted for the treatment of Parkinson's and depression, but not for the treatment of post-traumatic syndrome. The electrode was inserted into the ACC area, and conditioned its activity during the memory extinction process. In the test done the next day, it became clear that while the experimental animals that did not receive the treatment showed signs of strong distress upon hearing the sounds, animals that received the treatment reacted moderately. The stronger the suppression of ACC activity by the electrode was, the calmer the response was the next day, and even after three days. The findings of this study have been published In the journal Journal of Neuroscience.

The conventional clinical method for treating traumatic memories - which tries to eradicate the emotional context through behavioral therapy only - is in many cases ineffective and not durable for a long time, and the negative emotional memory keeps resurfacing. Dr. Paz's findings point to a possible mechanism responsible for the problem: the ACC area, which mobilizes to "make order" in a complex and uncertain picture of reality, fixes the memories in a way that makes it difficult for them to think. Understanding the mechanism by which it works will help not only to eradicate difficult memories, but perhaps even to strengthen and preserve the memories we want to remember.

2 תגובות

  1. It is interesting whether this discovery will cause people who have received a diagnosis of post-traumatic stress disorder to heal.

    In light of the secondary profit they have from their situation. that sometimes it is legitimate in society, that the individual is valued according to his achievements.

    And in light of this, a traumatic event causes crossroads thinking. That is, soul-searching about the meaning of life. and if

    The individual does not have a satisfactory answer for him, he surrendered himself to the phenomena of the post-trauma.

    If there is indeed a cure that will help some of the people who received a diagnosis of post-traumatic stress disorder, there will be no place for treatment

    The psychological which in most cases does not help. Kudos to the researchers.

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