Altered Structural-functional Maturation of the Right Amygdala in Healthy Adolescents Exposed to Traumatic Events

Abstract

Trauma is defined as a physical or psychological threat or assault to an individual's physical integrity, sense of self, safety or survival or to the physical safety of a significant other. The most common long-term mental health conditions resulting from trauma are post-traumatic stress disorder (PTSD) and depression. A number of studies using neuroimaging methodologies have implicated the amygdala and hippocampus in emotion processing in mood disorders, and adult depression studies suggest amygdala-hippocampal functional connectivity deficits. However, while trauma contributes to depression in a variety of ways, the neurobiological mechanisms underlying exposure to traumatic experiences have been poorly studied. In order to address this question, we used voxel based morphometry (VBM) and spectral dynamic causal modelling (spectral DCM; spDCM) approaches to analyse structural and restingstate functional magnetic resonance imaging and examine grey matter volume, white matter volume, and effective connectivity within the amygdala-hippocampal network in adolescents without psychiatric diagnoses, who had or had not been previously exposed to traumatic life events. Our results indicated greater intrinsic connectivity within the right amygdala in individuals with traumatic experiences compared to controls. Likewise we observed reduced white matter volume within the same region in those individuals, compared with controls. Together, these findings are suggestive of altered maturation of the right amygdala in healthy adolescents following trauma exposure. We interpret such brain changes as a plausible mechanism that may make individuals more vulnerable to developing psychopathology later in life.