How Are Brain Cells Affected When Traumatic Memories Are Removed?

Principal investigator: Dr Johannes Gräff

Institution: Ecole Polytechnique Fédérale de Lausanne

Funding Period: 2016-2019

Almost two million people in the UK live with post-traumatic stress disorder (PTSD), which can be caused by anything from military combat to traumatic childbirth.

The condition can cause serious and lasting distress, but remains difficult to treat – often because memories of traumatic events are deeply ingrained.

The project

Dr Johannes Gräff examined what exposure therapy can teach us about treating post-traumatic stress disorder (PTSD).

He investigated how brain cells are affected when the shadow of traumatic memories is successfully lifted.

This research is crucial for improving understanding and treatment options for anxiety and stress-related disorders, such as PTSD. The project has expanded from initial findings in the hippocampus to include the amygdala and prefrontal cortex, both key regions in traumatic memory processing. A near brain-wide map of areas active during remote fear memory attenuation has also been generated

The process

Johannes focussed on one of the most effective treatments for PTSD – exposure therapy. This involves helping people to overcome anxiety by exposing them to the source of their fears in a safe environment.

By pinpointing the brain cells involved in exposure therapy, Johannes studied how cell behaviour changes when traumatic memories are successfully targeted and reduced.

Cross-section of the hippocampal region within the brain showing nerve cells (green and red) activated by a traumatic memory

The outcome

Johannes’ study uncovered the group of cells vital for storing and reducing traumatic memories – offering hope for testing new interventions.

His results support the notion that re-writing memories – by facing fears – could be the most successful way to overcome a trauma, rather than trying to rationalise or suppress them.

Key Findings:

- Remote traumatic memory attenuation involves reactivation and updating of the original fear memory trace towards safety, rather than suppression;
- This process is mediated by a discrete subset of excitatory neurons in the hippocampus, amygdala, and prefrontal cortex;
- These neurons show a neuroplasticity-promoting epigenetic signature (increased histone acetylation);
- The findings support the concept of “reconsolidation-updating” at a cell population-specific level, providing the first evidence for this mechanism.

Papers published

Khalaf O, Resch S, Dixsaut L, Gorden V, Glauser L, Gräff J. Reactivation of recall-induced neurons contributes to remote fear memory attenuation. Science. 2018

The impact

Scientific Impact: The research provides neuroscientific proof that confronting fears (rather than suppressing them) is effective, supporting long-standing psychological theories with cellular evidence;

Clinical Relevance: These insights could inform new treatments for PTSD and related disorders by targeting the mechanisms of memory updating;

Recognition: The work has been well received in the scientific community and is expected to contribute to future academic and clinical advancements.

Dr Johannes Gräff

Dr Johannes Gräff focuses on neuroepigenetics – looking at how gene expression changes in response to environmental influences, like psychological therapies.