Traumatic Memories Present Differently Than Sad Memories in the Brain

The representation of traumatic memories in the brain differs significantly from that of depressing recollections, according to a recent study of the brain activity of individuals who have post-traumatic stress disorder (PTSD).

The research, published in Nature Neuroscience, lends credence to the idea that traumatic memories in PTSD represent a distinct cognitive entity that differs from ordinary memory, and it could offer a biological explanation for why traumatic memory recall manifests in PTSD patients as intrusions that are very different from regular negative memories.

PTSD is a mental illness that can develop in specific individuals who have been through a frightening, frightening, or hazardous situation. It's normal to experience fear both during and after a distressing event.

To connect personal experience to brain function, the study — conducted by scientists at Yale University and the Icahn School of Medicine at Mount Sinai — was also the first to examine participants' actual personal recollections instead of fundamental cognitive processes.

Until now, the reasons for the difference in these memories have been poorly understood.

Traumatic and sad memories: How do they differ?

According to their findings, the brain does not process traumatic memories like ordinary memories. They may not even be memories at all.

The generation and retrieval of episode memories are regulated by the hippocampal area of the brain, according to a prior study. The hippocampus is known to have anatomical abnormalities, primarily a reduction in volume, and the pathophysiology of PTSD is mainly focused on impairments to hippocampal functions.

It has been shown that the posterior cingulate cortex (PCC) plays a significant role in autobiographical processing, especially emotional memory imagery, as well as narrative comprehension. Specific to PTSD, changes in PCC connection and function are altered.

To investigate whether and how the hippocampus and posterior cingulate cortex distinguish between traumatic and happy autobiographical memories, 28 PTSD patients had their autobiographical memories reactivated using script-driven imagery during functional magnetic resonance imaging (fMRI).

First, the researchers employed an imagery generation process to produce stimuli based on the unique autobiographical recollections of each subject.

There were three categories in the study: the "PTSD" condition, the "sad" state is a significant but non-traumatizing experience; and the "calm" condition is a peaceful, happy occurrence. The participants expounded on these three categories of autobiographical recollections.

These intimate portraits of autobiographical memory were then methodically put together into a 120-second audio clip that a research staff member presented.

Additionally, to control for both content and arousal, the PTSD and depressing storylines were structured to optimize their structural resemblance to one another. FMRI was performed on participants as they listened to this unique interpretation of their memories for the first time.

The researchers postulated that neural similarity among PTSD subjects would follow from semantic similarity in personal recollections. If two people had comparable patterns of neural responses when listening to audio recordings of their experiences, then their neural responses should also be similar.

The researchers anticipated finding a semantic-to-neural correlation in both pairs of traumatic and sad memories, assuming that they are distinct instances of autobiographical memories.

Semantically equivalent sad sentences evoked similar neural representations in the hippocampus when seen by fMRI across subjects.

On the other hand, personal recollections of trauma that had a similar theme did not generate identical images.

Notably, the researchers also discovered a positive correlation between the semantic content of the traumatic narratives and neural patterns in the PCC, a part of the brain that has lately been described as a cognitive bridge between self-representation and external events.

The study pinpoints the neurological underpinnings of the disparate subjective experiences associated with recalling traumatic versus ordinary memories.

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