Brain Glitch or Survival Tactic? Why Traumatic Memories Behave Differently

Ever feel a happy memory fade but a bad one replays on repeat? Science explains why, and reveals a groundbreaking discovery that could transform how we treat trauma.

Written By: Saanvi Reddy

Picture this: you’re at a party, reminiscing with friends about that time you all got chased by a rogue squirrel in the park. Laughter fills the air as you relive the moment, but then someone mentions a darker memory — a moment that sends chills down your spine and silence through the room. It’s like a switch flips in your brain, and suddenly, the joyous chatter becomes a distant hum. Well, researchers at Yale University and the Icahn School of Medicine at Mount Sinai have just pulled back the curtain on why traumatic memories seem to have a VIP section in our brains while others are left waiting in line.

Imagine your brain filing memories like folders. Traumatic experiences are like emergency files. During a trauma, the amygdala triggers a stress response, essentially labeling the event “super important for survival!” This bypasses usual memory processing and stores the memory in a raw, emotional state, making it easily accessible but difficult to organize or control.

Before digging deeper into this recent study, let’s explore the topic of traumatic memories and what has been researched about them in the past. We have known for a while that people who live through traumatic events experience post-traumatic stress disorder (PTSD), where they go through nightmares, flashbacks, anxiety, and even feelings of isolation or guilt. But what really goes on in our brains when we have traumatic memories? It had been assumed that with PTSD patients, inside their brains, their amygdala activity (processing center for emotions) becomes heightened, causing a fear response. For PTSD patients, amygdala activity becomes hyperactive where something as simple as a slammed door can trigger panic. The hyperactive amygdala overwhelms the prefrontal cortex, which normally regulates emotions and makes decisions, leading to difficulty controlling reactions to trauma reminders. Additionally, the hippocampus, crucial for memory consolidation, can be affected in PTSD, resulting in fragmented or intrusive memories that further fuel the fear response. Chronic stress, as seen in PTSD patients, can also lead to hippocampal shrinkage through reduced neurogenesis and dendritic atrophy. This impacts memory processing and contributes to repetitive traumatic memory recall.

In a research study conducted by researchers at Yale University and the Icahn School of Medicine at Mount Sinai, 28 participants diagnosed with PTSD, were asked to elaborate on three types of their own memories: traumatic memories (sexual assault, combat, etc.), instances of sadness (death of a family member or pet), and a positive, calm event (something memorable from their lives). These descriptions were then made into 2 minute long audio clips where the research staff would narrate this story to the participants. The participants would hear the narration for the first time while undergoing functional magnetic resonance imaging (fMRI). This was used to observe the brain activity of the participants by tracking their blood flow. When a brain region is active, it requires more oxygen, which leads to an increase in blood flow to that area. By measuring these blood flow changes, fMRI can create a map of brain activity while a person performs a task or thinks about something.

The research team believed that participants who shared memories with similar meanings (semantics) would also show similar patterns of brain activity when listening to recordings of those memories. The researchers found that when the participants recalled any sad or neutral memories, their hippocampus showed similar activity among all the participants, showing a normal response to memory formation. When individuals recall past experiences, their hippocampus will activate to retrieve and reconstruct those memories.

However, when the participants were asked to recall traumatic events, the hippocampus showed fragmented and disorganized activity. The scripts between sad memories and traumatic memories were not the same. They found neural patterns in the posterior cingulate cortex (PCC) when the participants listened to the audio clips of their traumatic memories. The more severe the traumatic event, the more neural activity was seen in the PCC. Strangely, the PCC is not usually correlated with memory. It is mostly associated with internal experiences, meaning it is involved in activities like thinking about ourselves, our activities, or any plans for the future. So, the study showed how traumatic memories aren’t in a state of memory, but rather in a state of the present experience.

So what does this mean?

This was the first study to actually show neurobiological reasons for the difference in brain activity between different types of memories. Current research hints that for traumatic memories, the PCC plays a bigger role, opening the doors for more targeted research on PTSD treatment. Can we manipulate brain activity in the PCC to weaken negative memories, or can we strengthen the hippocampus to integrate traumatic experiences into a broader narrative? These are just some of the exciting avenues that this new knowledge opens.

Furthermore, this discovery challenges us to redefine “traumatic experiences.” Could chronic stress or racial trauma activate the PCC in ways similar to car crashes or war? A broader definition could ensure everyone who needs help receives it. This shift towards more specific treatment based on the brain region involved offers a beacon of hope for those struggling with PTSD. Treatments like Eye Movement Desensitization and Reprocessing (EMDR) might be refined to specifically target the PCC, potentially making them more effective and faster. Additionally, this research not only opens doors for more targeted PTSD treatments, but it may also lead to earlier identification of individuals at risk. Understanding the brain activity patterns associated with traumatic memories may help us develop screening tools to identify those who have experienced trauma and may benefit from intervention before symptoms worsen.

References:

• “Traumatic Memories Are Represented Differently Than Regular Sad Memories in the Brains of People With PTSD, New Research Shows.” Mount Sinai, 30 November 2023, https://www.mountsinai.org/about/newsroom/2023/traumatic-memories-are-represented-differently-than-regular-sad-memories-in-the-brains-of-people-with-ptsd-new-research-shows. Accessed 10 March 2024.
• Hathaway, Bill. “Study reveals distinct brain activity triggered by memories of trauma.” YaleNews, 30 November 2023, https://news.yale.edu/2023/11/30/study-reveals-distinct-brain-activity-triggered-memories-trauma. Accessed 10 March 2024.
• Barry, Ellen. “Brain Study Suggests Traumatic Memories Are Processed as Present Experience.” The New York Times, 30 November 2023, https://www.nytimes.com/2023/11/30/health/ptsd-memories-brain-trauma.html. Accessed 10 March 2024.
• Gardner, Christopher. “Neural Patterns Differentiate Traumatic From Sad Autobiographical Memories in PTSD.” Yale School of Medicine, 30 November 2023, https://medicine.yale.edu/news-article/neural-patterns-differentiate-traumatic-from-sad-autobiographical-memories-in-ptsd/. Accessed 10 March 2024.
• Dowling, Elizabeth. “Brain Activity in PTSD: Trauma Memories Differ from Sad Ones.” Neuroscience News, 30 November 2023, https://neurosciencenews.com/ptsd-sad-trauma-memory-25286/. Accessed 10 March 2024.