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Below, we have highlighted key findings from John France's paper on Anxiety, Fear Extinction, and Threat Related Amygdala Reactivity in Children Exposed to Urban Trauma.
DOI (main paper): https://journals.sagepub.com/doi/10.1177/20438087221132501
In our previous post, we discussed that the amygdala is one of the important brain regions that assesses danger and initiates a fear response. To study this, our lab is looking at whether childhood trauma exposure is associated with changes in amygdala reactivity to a social cue, for example a picture of a human face. Using a brain scanner (a functional magnetic resonance imaging or “fMRI” machine) we measured amygdala activity while 9-year-old children looked at pictures of faces with either a neutral or a scared expression, for less than a second.
Courtesy of our participant
The results showed that regardless of whether the child saw a neutral or fearful face, the activity in the amygdala was higher in children with higher anxiety symptoms such as breathing rapidly, feeling restless and having difficulty with concentration. The figure below shows both the part of the brain that was reactive to the faces (A), as well as the relationship between anxiety symptoms and amygdala activity. (B). This tells us that anxiety in childhood is associated with an exaggerated fear response to social cues (specifically faces). Furthermore, this increased fear response is misaligned to actual threat as children with higher anxiety had higher amygdala activity even to the neutral faces. This may mean that children exposed to trauma are more likely to judge neutral or ambiguous situations as threatening and have difficulty discriminating safe and danger signs. This neural signature may help clinicians and researchers to identify and treat children who are at risk for anxiety disorders and post-traumatic stress disorder (PTSD) later in life.
The graph on the left shows a child’s brain activity in response to fearful and neutral faces. Figure 1A shows brain images with activated amygdala regions in orange in response to fearful and neutral faces. Figure 1B shows the positive relationship between bilateral amygdala activation and anxiety symptoms.
The other important finding from this study was that amygdala responses during fearful face presentation increased across the brain imaging session. Usually, our brain response tends to decrease over time to the same type of stimuli such as faces. But our analysis showed that children did not show this habituation effect; instead, they showed heightened amygdala response over time. These findings may reflect that children with trauma exposure have brains that pay extra attention to potentially threatening cues, which may be a survival mechanism to help them avoid danger in the future.
Overall, this study suggests that changes in amygdala reactivity may be a marker of fear circuit hyperactivity in children with trauma exposure. In the future, we might be able to use brain scans of amygdala reactivity to identify children at risk for trauma related disorders, and thus provide treatment at more precise and beneficial periods in life. The next blog post will be looking at how childhood trauma is related to resting state brain activity in cognitive regions such as hippocampus and insula.