A new scientific review is shedding light on memory engrams in PTSD—the tiny, scattered clusters of brain cells that hold the key to how we store and relive memories. Scientists are beginning to map out how these engrams form, how they generalize over time, and how they can be reshaped. This work could change the way we treat post-traumatic stress disorder (PTSD) and other anxiety-related conditions.
What Are Memory Engrams?
Engrams are groups of neurons that undergo physical and chemical changes to lock in a memory. They act as the biological traces of experiences, from joyful moments to traumatic events. These neurons become part of the memory trace through a kind of internal “competition,” where the most excitable neurons are recruited during learning.
Recent advances in neuroscience now allow researchers to label and even activate these neurons, letting them observe memory formation in real time. With tools like optogenetics and genetic tagging, scientists can trigger a specific memory by stimulating the right neurons—even without external cues.
How Memories Move and Morph
Memories don’t stay in one place in the brain. Right after an experience, a memory starts out in the hippocampus—a brain region tied to context and emotion. Over time, however, that memory shifts to the cortex through a process called systems consolidation. This transfer helps turn a detailed memory into a more generalized one.
This transformation is useful for learning. It helps us apply past experiences to new situations. But in PTSD, this same process can go too far.
When Memory Generalization Becomes Harmful
The role of memory engrams in PTSD symptoms
In PTSD and anxiety disorders, memories can become overgeneralized. Instead of remembering a specific traumatic event, the brain responds with fear to any similar situation—even when there's no real threat. This happens when the hippocampus, which helps keep memories specific, stops working properly due to chronic stress or trauma.
This can result in constant anxiety, panic attacks, or avoidance behaviors triggered by non-threatening reminders of the past. Overgeneralized fear responses are one of the hallmark features of PTSD.
Can We Change the Emotional Weight of a Memory?
One of the most exciting discoveries in memory research is that memories aren’t fixed. When a memory is recalled, it enters a temporary “editing mode” where new information or emotional tones can be added. This process is called memory updating.
If researchers can find safe, targeted ways to modify memory engrams without deleting core experiences, it could lead to new treatments. Instead of suppressing traumatic memories, therapies might one day rewire their emotional charge—reducing fear and distress while preserving the memory itself.
What Comes Next?
Scientists are still investigating how these cellular memory processes interact with our mood, decision-making, and mental health. Questions remain: How do neurons enter and exit memory networks? How do stress and life experiences reshape our brain’s storage system? And how do we preserve memory flexibility without losing stability?
As researchers learn more about memory engrams in PTSD, the possibility of creating targeted, brain-based therapies grows closer. We may soon be able to help people reframe their past, not by forgetting it, but by changing how it feels.
Discover more at https://interventionalpsychiatry.org/
Citations:
Chen, Z.-Y., Teng, S.-W., & Zhang, Z. (2025). Dynamic memory engrams: Unveiling the cellular mechanisms of memory encoding, consolidation, generalization, and updating in the brain. Brain Medicine. https://doi.org/10.61373/bm025i.0044
Tonegawa, S., Pignatelli, M., Roy, D.S., & Ryan, T.J. (2015). Memory engram storage and retrieval. Current Opinion in Neurobiology, 35, 101–109. https://doi.org/10.1016/j.conb.2015.07.009
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