The neurons that rewrite traumatic memories

**The neurons that rewrite traumatic memories
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


Now, a new study shows—at the cellular level—how therapy can treat even long-term memories of trauma. "Our findings shed, for the first time, light onto the processes that underlie the successful treatment of ," says EPFL Professor Johannes Gräff, whose lab carried out the study.

In the field of treating traumatic memories there has been a long-debated question of whether attenuation involves the suppression of the original trace of fear by a new memory trace of safety or the rewriting of the original fear trace towards safety. Part of the debate has to do with the fact that we still don't understand exactly how store memories in general. Although they don't exclude suppression, the findings from this study show for the first time the importance of rewriting in treating traumatic memories.

Research in this area focuses on understanding the brain's capacity to reduce traumatic memories, but surprisingly few studies have investigated treatment options for attenuating long-lasting trauma (aka "remote fear") in animal models.

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, the scientists have located these neurons in the brain's , 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 "reporter" gene 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 subpopulation of neurons in the dentate gyrus that are involved in storing long-term traumatic memories.



Finally, when the researchers enhanced the excitability of these recall neurons during the therapeutic intervention, they found that the showed improved fear reduction. Thus, they concluded that attenuating remote fear memories depends on the continued activity of the neurons they identified in the dentate gyrus.

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More information: Ossama Khalaf, Siegfried Resch, Lucie Dixsaut, Victoire Gorden, Liliane Glauser, Johannes Gräff. Reactivation of recall-induced neurons contributes to remote fear memory attenuation. Science 15 June 2018. DOI: 10.1126/science.aas9875
Journal information: Science

Citation: The neurons that rewrite traumatic memories (2018, June 14) retrieved 11 December 2019 from https://medicalxpress.com/news/2018-06-neurons-rewrite-traumatic-memories.html

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