Most of us have heard that memory works like a reconstruction project: every time we recall something, we piece it together from fragments rather than pressing play on a perfect recording. That’s why memories can change over time and why they are sometimes unreliable.
But new research on how the brain stores traumatic events shows this isn’t the whole story. When a memory carries strong emotion, especially fear or threat, the brain seems to replay the original pattern rather than rebuild it. This may be why traumatic memories are so hard to change and why they can feel frozen in time.
What the Scientists Did
Researchers recorded brain activity directly from two key areas:
- The amygdala, the brain’s emotional alarm system
- The hippocampus, the brain’s memory hub
Participants viewed both neutral and emotionally intense (aversive) images. A day later, they were tested on what they remembered, with brain activity recorded again during recall.
What They Found About How the Brain Stores Traumatic Events
- An emotional “stamp” at encoding: When participants saw aversive images, the amygdala sent out brief bursts of high-frequency activity, almost like a neural stamp marking the moment. The hippocampus picked up this stamp as it stored the memory.
- Replay during recall: A day later, when those aversive images were remembered, the hippocampus replayed the same pattern it had received from the amygdala, almost like pressing play on an old recording.
- Not true for neutral memories: This replay pattern was specific to emotional images; neutral memories didn’t show the same effect.
- A mixed picture: At a broader level, brain activity still changed between learning and remembering, which fits with the reconstruction view. But those emotional “stamps” remained and were replayed.
Why This Matters
This study bridges two ideas:
- Memory is often reconstructive and flexible.
- Yet certain emotional memories are partly replayed rather than rebuilt.
For coaches and therapists, this helps explain why traumatic memories are so hard to change:
- They are “stamped” in. The brain replays the original emotional imprint rather than entirely rewriting it.
- They stay emotionally charged. The hippocampus replays the amygdala’s signal, which keeps the memory vivid even long after the event.
Implications for Change Work
If emotional memories are partly replayed, changing the story alone may not be enough. We may also need to shift the emotional state connected to the memory. For example:
- Calm the body and nervous system before recalling a difficult event
- Pair the memory with a new, safe, or positive experience to help the brain update it
- Work gradually so the emotional stamp can soften over time
Key Takeaway
Understanding why traumatic memories are so hard to change gives us new insight into how the brain stores traumatic events. It shows that memory is not always a simple reconstruction. Sometimes, especially with emotional memories, the brain hits replay. This helps explain why aversive memories can be so persistent and why effective change often begins with shifting the emotional state, not just the story.
Reference:
Costa, M., Pacheco-Estefan, D., Gil-Nagel, A., Toledano, R., Imbach, L., Sarnthein, J., & Strange, B. A. (2025). Human hippocampal reactivation of amygdala encoding-related gamma patterns during aversive memory retrieval. Nature Communications, 16(1), 6820. https://doi.org/10.1038/s41467-025-61928-2