In vivo structural analyses of amygdala subregions in relation to stressful life events: A systematic review

Exposure to stress, particularly during childhood, has been linked to chronic medical conditions, including mental disorders. In recent years, advancements in modern segmentation techniques for magnetic resonance imaging (MRI) have allowed for more detailed study of brain regions in vivo. While automated segmentation of the hippocampus has been a well-established method, the segmentation of the amygdala has been implemented relatively recently. Despite the importance of the amygdala in stress processing, to our knowledge, no literature review has been conducted on the volumes of amygdala subregions in relation to stressful events in human subjects in vivo. In this review article, we provide a systematic review of the studies of amygdala subregions volumes in the presence of exposure to stressful life events. Our findings show that studies of amygdala subregions in human subjects in vivo predominantly reported an inverse association of their volumes with exposure to stressful events. Specifically, the nuclei within the basolateral complex were most frequently reported, followed by the superficial structures. Positive associations were less frequently reported. Overall, this review provides valuable insights into the relationship between amygdala subregion volumes and exposure to stressful events in human subjects in vivo. The currently available evidence provides no strong support, that some amygdala subregions are more likely to be stress sensitive than others. The findings could help designing future studies on associations of exposure to stressful events and brain structure.