News release

From: Springer Nature

Neuroscience: Identifying traumatic and sad memories in individuals with PTSD

Neural representations of traumatic memories in the brain differ from those of sad, non-traumatic memories in individuals with post-traumatic stress disorder, a paper in Nature Neuroscience reports.

A traumatic, personal memory is at the core of post-traumatic stress disorder (PTSD). Previous research has mainly focused on using non-personal learning and memory-related tasks to try and establish what makes certain memories traumatic. However, research has yet to address the nature of personal, real life, traumatic memories, and how they differ from sad, non-traumatic autobiographical memories.

To investigate how these memories differ, Daniela Schiller, Ilan Harpaz-Rotem, Ofer Perl, and colleagues recruited 28 participants with PTSD, and recorded their neural responses with functional MRI while they listened to two-minute narrative clips. These clips were of their own memories—traumatic memories associated with their PTSD, sad but non-traumatic memories, and calm memories—and were designed to have the participants reactivate each kind of memory.

The authors analyzed the semantic similarity of the memory narratives, and they found higher semantic similarity across traumatic and sad memories relative to the calm ones, suggesting both types of negative memories had themes in common. When the authors examined neural activity from the hippocampus, the amygdala, and the posterior cingulate cortex (regions that are involved in processing traumatic memories in PTSD) they found that when participants had similar sad autobiographical memories (such as a death of a family member) they also had similar neural representations in the hippocampus. However, this was not observed for traumatic memories, despite the semantic similarity to the sad autobiographical memories. Neural responses to the narratives in the hippocampus could also be used to decode whether sad or traumatic memories were reactivated. Additionally, the authors indicate that more-severe PTSD was associated with a stronger link between semantic and neural similarity for traumatic memories specifically within the posterior cingulate cortex, but not within the other two brain regions.

The authors note that further research is needed in larger cohorts but suggest that their findings could demonstrate that the brain may represent traumatic memories differently from similar sad memories in individuals with PTSD.