A new study has shed light on how the brain processes traumatic memories in people with post-traumatic stress disorder, finding that a region long thought to play little role in trauma recall is in fact actively involved. The research offers a more detailed picture of what happens neurologically when someone with PTSD revisits a traumatic experience, with implications for how therapy is understood and refined. The findings were published in Neuropsychopharmacology.
Scientists at the University of Texas at Austin and the University of Wisconsin at Madison scanned the brains of 79 women who had developed PTSD following interpersonal violence. Using functional MRI technology, participants listened to audio recordings of their own traumatic experiences as well as neutral autobiographical memories while researchers tracked activity across specific brain regions in real time.
The team applied a form of artificial intelligence known as a sentence transformer to analyse the meaning of each sentence in the narratives. This allowed them to map, sentence by sentence, how different parts of the brain responded to the specific content of the memories rather than simply reacting to the emotional tone of the story as a whole.
The hippocampus, a structure in the brain’s medial temporal lobe associated with memory retrieval, showed measurable sensitivity to the semantic content of both traumatic and neutral narratives. This challenges an earlier influential finding that suggested the hippocampus plays no meaningful role in processing traumatic memories and that trauma memory operates as a fundamentally different kind of cognitive experience.
While the hippocampus responded to both memory types, the spatial patterns of activity within it differed depending on whether the memory was traumatic or neutral. Two specific subregions, known as CA1 and the dentate gyrus, showed distinct encoding patterns for the two narrative types. The dentate gyrus is involved in functions including pattern separation and novelty detection, while CA1 has been linked to autobiographical memory and fear extinction learning.
The study also found that greater severity of PTSD symptoms was associated with stronger hippocampal sensitivity to the semantic content of both traumatic and neutral memories. This suggests the hippocampus may be broadly more reactive in people with more severe PTSD, not just during trauma-specific recall.
Outside the hippocampus, the left superior temporal gyrus showed heightened sensitivity to trauma narrative content, consistent with its known role in language processing. The posterior cingulate cortex, a hub of the brain’s default mode network, showed reduced encoding during trauma recall compared to neutral memory, possibly reflecting suppression of internally directed thought when trauma-related material demands attention.
The researchers note that the findings carry relevance for treatments such as prolonged exposure therapy, which ask patients to repeatedly narrate and revisit their trauma. The results suggest this process actively engages the hippocampus in a way that may support the extinction of fear responses and the gradual recontextualisation of traumatic experiences.
The sample was restricted to women with PTSD related to interpersonal violence, and the study’s authors acknowledge that the effects, though statistically significant, were modest in magnitude.