The Neurons That Rewrite Traumatic Memories

Source: Ecole Polytechnique Federale de Lausanne

Summary: For the first time, a new study finding shed light on the processes that underlie the successful treatment of traumatic memories.

Memories of traumatic experiences can lead to mental health issues such as post-traumatic stress disorder (PTSD), which can destroy a person’s life. It is currently estimated that almost a third of all people will suffer from fear-or stress-related disorders at some point in their lives. In the field of treating traumatic memories, there has been a long-debated question of whether fear attenuation involves the suppression of the original memory trace of fear by a new memory trace of safety or the rewriting of the original fear trace towards safety. Research in this area focuses on understanding the brain’s capacity to reduce traumatic memories. Researchers from the University of Ecole Polytechnique Federale de Lausanne has found that how therapy can treat even long-term memories of trauma at the cellular level. The study findings were published in the journal Science.

Post-traumatic stress disorder

Cross section of the mouse hippocampus – a brain region involved in learning and memory – indicating in green cells that are active when mice recall a 1-month-old traumatic memory, and in red cells that are active when mice underwent an extinction training, which resembles exposure therapy in humans. Credit: EPFL / Gräff Group

The EPFL scientists found that remote fear attenuation in the brain is connected to the activity of the same group of neurons that are also involved in storing these memories. Working with mice, they have located these neurons in the brain’s dentate gyrus, an area of the hippocampus that is involved in the encoding, recall, and the reduction of fear. The mice used in the study are genetically modified to carry a “reportergene that produces an identifiable and measurable signal, e.g. a fluorescent protein, following neuronal activity. Using a fear-training exercise that produces long-lasting traumatic memories, the scientists first identified the sub-population of neurons in the dentate gyrus that are involved in storing long-term traumatic memories. They concluded that attenuating remote fear memories depends on the continued activity of the neurons they identified in the dentate gyrus.

Prof. Johannes Gräff said, “Our findings shed, for the first time, light onto the processes that underlie the successful treatment of traumatic memories.”

More Information: Ossama Khalaf et al, “Reactivation of recall-induced neurons contributes to remote fear memory attenuation” Science (2018). DOI: 10.1126/science.aas9875 

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