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Fear: Replacing Memories

The human brain goes through a complex process to form and consolidate memories. But is it possible to replace memories of fearful events, and in doing so, assist in the treatment of patients suffering from the debilitating effects of post-traumatic stress disorder or other anxiety disorders? Dr.Joseph LeDoux and a team of New York University neuroscientists think they have found a way to replace traumatic memories through therapy.

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Introduction: Welcome to “Speaking of Science”, the National Institute of Mental Health presents a series of conversations with innovative researchers working in a wide range of disciplines to pave the way for the prevention, recovery, and cure of mental illness.  

Narrator: We all have difficult sometimes painful memories stored in our minds. Memories most of us are able to come to terms with, but for some people the trauma of experiencing danger, violence, or panic can create a debilitating disorder. What if fear memories could be rewritten?

Dr. LeDoux: All of this research was based on systemic manipulations of the brain.

Narrator: Dr. Joseph LeDoux is a Professor of Science at New York University and serves as Principal Director for the NIMH funded Center for the Neuroscience o f Fear and Anxiety. He is part of a team that has found a way to block fear memories through a process called reconsolidation. During a recent visit to the NIMH campus in Bethesda, Dr. LeDoux explained the key to reconsolidation is understanding how memories are formed in the first place.

Dr. LeDoux: Each time you form a memory your brain begins to form that memory in a temporary way that can be interfered with if nothing else happens. So you have to convert a temporary memory into a long term memory in order to have that memory at some time in the future.

Narrator: In 1999 a study from the LeDoux team showed the ability to block the consolidation of fear memories by injecting Protein synthesis inhibitors to stop growth of certain cells in the amygdala, the brain’s fear hub.

Dr. LeDoux: So that led Graham Nader who was in my lab at the time say well can we do the same with reconsolidation? Which means, instead of giving the protein synthesis inhibitor after learning and blocking consolidation, you give it after the retrieval of a previously consolidated memory? So you form the memory, the animal now has a long term memory and then at some point after that memory is fully established, you give the rat the tone which retrieves the memory and then you give the protein synthesis inhibitor and then you test the animal the next day and the memory is no longer there. It’s like a person who goes to trial to testify about a crime and instead of testifying about what they witnessed on that day they testify about what they read in the newspaper. Because each time you take a memory out of a newspaper reading, you restore it and the information gets stored as a new memory. So the bottom line of all this research is-- your memory is only as good as your last memory.

Narrator: Perhaps the greatest potential for therapeutic application is with post traumatic stress disorder patients.

Dr. LeDoux: Where a patient with intrusive memories could be through the aid of a therapist and the aid of proper manipulations such as a drug that is safe to use with humans. The patient could be encouraged to retrieve the traumatic memory, given the manipulation and presumably the memory will be weakened at a later point.

Narrator: In December, a new study was published in Nature from a larger NYU research team that showed a drug-free method of replacing fear memories in people using exposure training. Dr. LeDoux acknowledges ethical questions when it comes to the science of altering memories.

Dr. LeDoux: I understand why people worry about that because memories are treated as sacrosanct; we are our memories in many ways. We have to remember who we are to be that person from day to day. But one thing we have to realize is just how much we manipulate memory as part of life. Every time we watch an ad for a product our memory is being manipulated, every time a student goes to class his or her memory is being manipulated, every time you have a social interaction with a person you try to create a good impression which is basically a memory. Once we put it into that context the idea that you might use memory manipulation to help people maybe doesn’t seem so malevolent.