Trauma experienced early in life can lead to long-term health consequences across a lifetime by altering the brain's connectivity at a stage when it is most vulnerable. How the interconnectivity of different brain regions changes due to repeated trauma in adolescence and how that might mediate a mechanism that increases the risk of psychiatric disorders later in life is less well understood. 

A new study reported in Biological Psychiatry: Cognitive Neuroscience and Neuroimaging may have new clues. Using functional magnetic resonance imaging (fMRI), the researchers found alterations in functional connectivity (FC) of three important brain networks – the default mode network, the salience network, and the central executive network, known collectively as the triple network – in individuals who experienced repeated trauma early in life. These three brain networks play an important part in our emotional and stress regulation, cognition, perception, and social interaction.

“While negative health outcomes have been associated separately with early life victimization exposure, disrupted adolescent neurodevelopment, and aberrant neural network responses to acute stress, no previous research had examined how these factors are related to each other,” Dr Rachel Corr, the lead author, explained in a statement. 

Using fMRI, the authors of the new study wanted to test how the FC of the triple network might change under acute stress. fMRI measured blood flow in the brain while a participant was asked to perform a specific task in the scanner. Areas of the brain where more blood flow was detected are more active, and therefore provide researchers the ability to track parts of the brain that are functionally interconnected with each other. 

In the study, the authors examined previously collected fMRI data from a cohort of 79 children, between the ages of nine and 16, who had experienced varying levels of trauma in the past. 

In the control group, the researchers gave each participant a math problem to solve while scanning their brains. The participants could work at their own pace in the knowledge their answers wouldn't be recorded, providing a relaxing approach to the task. They then induced an acute stress condition: The second group was asked to perform the math problem quickly within a time limit and were given constant negative feedback about their performance while completing the test. 

The researchers found that participants who experienced the acute stress situation in the fMRI scanner had altered FC in the triple network compared to the control group. They saw an increase in FC between the default mode network and central executive networks and a decrease between the salience network and the other two networks. The researchers postulate that it might be a brain region called the insula, which is responsible for inwardly directed attention, that might be mediating the interconnectivity changes they saw. 

Moreover, those that had experienced repeated trauma in the past were also more likely to show a reduction in FC between the salience and default mode networks and the insula, suggesting that repeated trauma might induce a mechanism that makes the brain less able to react to stressful situations by alternating the interconnectivity between these important brain networks.

“This study shows how repeated trauma may lead to a maladaptive response to acute stress in important functional brain networks and reveals a potential mechanism by which multiple early life stressors may lead to increased neural vulnerability to stress and the associated liability to future mental health problems,” Cameron Carter, MD, Editor of the journal, concluded of the work.