This article was co-authored by Dr. Ruth Lanius and Lauren Rudolph
It’s what happens in our brain that makes us react traumatic Memories that even if we are safe, there is still danger? We spent a first-of-its-kind study comparing the brains of people with and without PTSD when they recall traumatic memories. The results were surprising and have important implications for treatment.
People with PTSD often struggle to feel safe and grounded when recalling traumatic memories, so we wanted to understand whether there are differences in the connections between different levels of the brain that contribute to this. This is the first study to look at the relationships across whole people recall traumatic memories instead of focusing on specific areas of the brain.
What we did in study
In this study, we asked the following question: What are the connections? across Are brain levels different in people with classic PTSD, in people with the dissociative subtype of PTSD, and in people who have experienced a traumatic event but not developed PTSD?
All participants remembered the neutral memory and traumatic memory during fMRI brain scans. Traumatic memory”moral injury” – a traumatic event associated with the need to act against one’s own code ethicsor witnessing someone else doing it. We compared two groups (those without PTSD and those without PTSD) and two types of memory (neutral memory and traumatic memory).
What we’ve discovered about PTSD
So what did we discover? We found that people with PTSD (classic PTSD and the dissociative subtype of PTSD) have weaker connections between different brain regions involved in coordinating thoughts, emotions, and physical responses. In people with PTSD, the survival brain (midbrain and cerebellum) is not sufficiently connected to the reflective brain (cortex), and these connections are critical to renewing someone’s sense of security.
In order to feel safe, the brain needs to update its predictions as needed. The cerebellum is an important prediction center that predicts how we will react to events. The cerebellum constantly compares what the brain expects with what actually happened. When a prediction about how we will respond (e.g., predicting that we will run) does not match the current sensory information (e.g., that we are frozen because we are motionless), the cerebellum tells the cortex that there is an error in the prediction. The cortex can then provide the cerebellum with updated information about what is happening in the present (eg, we are safe now) so that we can make better predictions next time. This is very important for him to feel truly safe after the trauma.
In PTSD, these areas of the brain are less connected, so the prediction centers are stuck with information from the past and don’t receive updated information that they are now safe.
Interestingly, when people with PTSD recalled traumatic memories, another change occurred in the cerebellum: increased connections. inside cerebellum. This means that instead of sending and receiving important updates from the cortex and other areas of the brain, the cerebellum (the prediction center) works on its own to signal that we are safe. Without these updates, a person is “stuck in the past” and does not contain information from our current situation. For example, the sound of fireworks causes the Veteran to run away despite hearing a loud explosion in a safe family gathering.
Our research also helped explain why people with the dissociative subtype of PTSD often feel disconnected when recalling traumatic memories or when confronted with reminders of the trauma. The brains of these people had weaker connections between important parts of the brain. Their visual information, sensory information, and body movement information did not communicate well.
This explains why people with dissociative PTSD may feel disconnected, even in the face of current sensory information that tells them they are safe. For example, if the brain didn’t connect what we see around us with what our body feels, it would be very confusing. Imagine trying to pick up a glass of water if you’re not sure where your hand is!
Implications for treatment
Overall, this research suggests that PTSD may involve problems with the brain predicting and processing one’s experiences. When recalling traumatic memories, the PTSD-affected brain may rely more on basic survival responses (eg, fight, flight, freeze). At the same time, it may rely less on the brain functions that help people notice the present and understand that a memory is in the past. This helps explain why traumatic memories in PTSD often feel so real and terrifying—they feel like they’re happening right now, right now. Changes in brain connections cause the brain to lose its ability to update information, leaving us stuck in the past.
To illustrate this, here is another example of how the brain reacts to a fearful situation:
If you take the same route to work every day, your brain predicts that you will be normally calm and tunes out irrelevant stimulation. However, if you’re almost hit by a car, this sudden experience creates a prediction error. It’s normal to be cautious around that intersection for the next few days.
Through vertical integration across the lower levels (brainstem and cerebellum) and higher levels (cortex) of the brain, your brain refreshes after a few safe trips and realizes that you are safe again.
However, the brain with PTSD does not update to safety. Instead, it gets stuck in the past and continues to predict the threat, in part because it lacks vertical integration across these levels of the brain.
This is important for treatment. This suggests that treatment should restore vertical integration to improve the brain’s ability to update information. It helps to restore the feeling that “I am safe”. We will publish another one Psychology today Post on treatment approaches that improve vertical integration coming soon – stay tuned!
