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EASY-TO-UNDERSTAND SUMMARY: MAJOR BRAIN NETWORKS
THAT ARE IMPACTED BY TRAUMA
Major Brain Networks
How does the brain change after eye movements, such as from EMDR?

Harricharan S, McKinnon MC, Tursich M, Densmore M, Frewen P, Théberge J, van der Kolk B, & Lanius RA (2019). Overlapping frontoparietal networks in response to oculomotion and traumatic autobiographical memory retrieval: implications for eye movement desensitization and reprocessing, European Journal of Psychotraumatology, 10:1, DOI: 10.1080/20008198.2019.1586265

Traumatic memories are frequently relived (e.g., in the form of images, sounds, smells, and/or physical sensations), and these experiences are referred to as “flashbacks”.  These flashbacks are typically accompanied by intense, negative emotions (e.g., terror, humiliation).  One effective treatment for PTSD, including flashbacks, is EMDR (Eye Movement Desensitization and Reprocessing), which involves the client steadily moving their eyes back and forth/left to right while recalling distressing memories (under clinician guidance, of course!).  Research shows that these eye movements, as part of therapy, can help reduce the fight/flight response (e.g., increased heart rate, breathing rate, sweating) caused by the memories, as well as their intensity and vividness.  In this study, we were hoping to learn more about how EMDR does this – what brain changes take place in association with these eye movements? 

 

For this study, we compared two groups of participants – adults with PTSD, and adults with no history of mental health diagnoses (our “control” group), who completed fMRI (functional magnetic resonance imagining) brain scans.  During these scans, participants were asked to recall either neutral or stressful/traumatic memories.  While they recalled their memories, they also viewed dots projected onto a screen that were moving side-to-side, and participants were asked to follow them with their eyes (replicating the eye movements made during EMDR). 

 

Based on the results of this study, we believe that, in individuals with PTSD, these horizontal eye movements may activate certain brain areas that help with emotion regulation – making the traumatic memory more manageable.  Further, we found unique brain patterns associated with dissociative symptoms (perhaps representing the more recently identified “dissociative subtype” of PTSD).  It may be that these unique patterns/differences interfere with certain “top-down” brain functions (e.g., emotion regulation, the interpretation of our experiences/events based on previous experiences). 

 

These differences may also help explain why dissociative symptoms can sometimes interfere with trauma processing.  More research will be necessary to fully clarify how EMDR helps treat PTSD, but these results help us understand the process a little bit better.

What is the role of 3 major brain networks, and what treatments help improve these networks in people with PTSD?

Lanius RA, Frewen PA, Tursich M, Jetly R, & McKinnon MC. (2015). Restoring large-scale brain networks in PTSD and related disorders: A proposal for neuroscientifically-informed treatment interventions. European Journal of Psychotraumatology, 6:1, 27313, DOI: 10.3402/ejpt.v6.27313.

As discussed in our other research summaries, there are important brain “networks” (i.e., brain areas that communicate with one another) called “intrinsic connectivity networks”, or ICNs. Three ICNs have been identified as being very important for more complex brain functions (e.g., reasoning, planning, and memory).  These ICNs are:  the central executive network (CEN - which is used in verbal learning, working memory, planning, etc.), the default mode network (DMN - which helps us process information about ourselves and interact socially with others), and the salience network (SN – which helps direct our behaviour to the most important actions needed).  Each ICN can also impact the others’ performance.  Research shows that the function of these ICNs is typically impaired in people with certain mental health disorders, including PTSD. 

Our goal for this paper was to summarize information from previous research regarding the roles of these networks, to better understand how they function in people with PTSD, and to consider treatments that may improve their function.  Review of the existing research (up to 2015) provided further evidence that the function of these brain networks is altered in people with PTSD.  Further, we saw potential connections between each network and specific symptoms of PTSD:  the CEN seems to be related to the cognitive problems observed in many individuals with PTSD (e.g., thinking, memory); the SN appears to be related to issues with hyperarousal (e.g., being overly watchful for danger), hypo-arousal (e.g., dissociation, spaciness), and poor body-awareness; and the DMN appears to be related to alterations in the sense of self (e.g., feeling very badly about oneself). 

A number of possible treatments thought to help restore the function of these three impaired networks were identified.  Neurofeedback, transmagnetic stimulation (TMS), and certain prescription medications have the potential to improve the function of all three ICNs.  The practice of mindfulness may help improve the function of the SN, and cognitive remediation (like training or rehab for thinking skills) could help improve the function of the CEN.  Finally, certain types of talk-therapy could be helpful in improving the function of the DMN. 

This review emphasized the importance of health care practitioners understanding the neuroscience of PTSD – in order to treat PTSD effectively, practitioners need to understand how the brain has been impacted by trauma and PTSD.

How is the brain's innate alarm system different in people with PTSD?

Terpou BA, Densmore M, Thome J,  Frewen P, McKinnon MC, Lanius RA.  The Innate Alarm System and Subliminal Threat Presentation in Posttraumatic Stress Disorder: Neuroimaging of the Midbrain and Cerebellum. Chronic Stress 2019; Volume 3: 1–13.  DOI: 10.1177/2470547018821496

The innate alarm system (IAS) is made up of a network of brain structures, and its job is to quickly detect danger in the environment, even before we become consciously aware of it (which is referred to as “subliminal” awareness).  This allows us to react more quickly to potential threats, helping to keep us safe.  For example, the IAS might cause us to jump back out of the way of a car when we’re trying to cross the street, even before we’re fully aware of it coming toward us.  The activity of this system is particularly interesting when considering PTSD because people with this condition tend to be easily startled, and they often struggle to “unlearn” defensive responses (e.g., fight/flight/freeze reactions), even when threats are no longer present. 
 
This study attempted to learn more about the impact of PTSD on the IAS.  Here, we compared IAS function in people with PTSD to people with no mental health diagnoses.  This was done using the fMRI brain scanner while showing participants triggering images (e.g., photos of strangers with fearful facial expressions, and personal trauma-related words).  More specifically, we were interested in learning how our participants’ brains reacted to subliminal triggers (i.e., pictures/words presented so quickly, the participants were unable to consciously see them). 
 
Our analysis suggested that the IAS is overactive in people with PTSD (i.e., they’re more sensitive, and more responsive to subliminal triggers).  We also observed that that their brain (specifically, their cerebellum - a structure in the lower brain area) struggled to regulate their defensive reactions. 
 
Overall, and understandably, PTSD seems to make someone more sensitive to potential threat, often causing their brain to react as if they’re in danger, even in safe situations.  You might say that, unlike seeing the world through rose-tinted glasses, people with PTSD tend to view the world through “danger-tinted” glasses, and that their brains and bodies automatically react to any perceived danger.  This may help explain the strong startle responses seen in people with PTSD, and their difficulty “unlearning” their fight/flight/freeze reactions.  Knowing these neurological differences, more effective treatments for PTSD can be developed and prescribed.

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