Hippocampal Memory Systems.
The hippocampus plays an important role in the formation and organisation of memories, particularly by helping to process the context in which events occur. Older memories become increasingly supported by distributed networks across the brain. The hippocampus is one of the key brain structures involved in memory formation and contextual processing. Studies indicate that PTSD is associated with disruptions in communication between the hippocampus and other brain networks involved in memory, emotion, and sensory processing.
Image Credit: Horizon/Keystone/SPL/Roger
Traumatic experiences affect how one thinks, feels, and remembers. During post-traumatic stress disorder, people experience the distress of memories of the trauma, flashbacks of the event, and the feeling that the trauma is recurring again. According to recent studies, trauma does not erase memories; it may be associated with changes in how the brain processes and connects these memories.
According to a recent study published by Chaposhloo, McKinnon, and co-researchers, the researchers investigated the way memories are processed in people who have suffered trauma and have PTSD and manifest dissociative symptoms. Dissociation may occur as a feeling of disconnection with the self, body, and the world. The researchers investigated the workings of the hippocampus. This brain region is known to play an important role in memory and understanding the time and place of the event that took place.
The study was based on two parts of the hippocampus: the anterior hippocampus, related to emotional memory, and the posterior hippocampus, related to processing contextual information and details of memories. By means of fMRI, during the active recall of traumatic memories versus neutral ones, the researchers studied three dostict groups: individuals with classic PTSD, PTSD patients with dissociative symptoms, and individuals who have experienced trauma without PTSD.
The research shows that PTSD is associated with variations in the functionality of the memory structure of the hippocampus and its connections with other brain structures at the moment of memory retrieval. The results show an important difference in the areas of the hippocampus: while the anterior part has a more active role during an emotional reaction in the conventional type of PTSD, the dissociative type is comprised of abnormal connections of the posterior area of the hippocampus. This affected connectivity includes structures involved in the sensory functions, awareness of the body, emotions, and memory processes. Since the posterior area fails to connect the memory to a specific time and space and associate it with the past experience, the person may feel as if the memory takes place again.
The conclusion can be drawn that trauma may influence memory processing by linking this experience with emotions and senses instead of simply erasing memory. The implications of the study suggest that trauma does not remove memories but may influence the way memories are connected and experienced.
The findings also emphasise that PTSD with dissociation may involve a distinct pattern of brain functioning compared with PTSD without dissociation, rather than simply being a more severe form of PTSD.
Reference:
Chaposhloo, M., et al. (2025). Unravelling trauma memory: Differential functional connectivity profiles of anterior and posterior hippocampus in post-traumatic stress disorder and its dissociative subtype. https://doi.org/10.1016/j.ynirp.2025.100279
