Pinpointing regional surface distortions of the amygdala in patients with spider phobia

The amygdala is a key brain structure involved in emotional processing, especially fear. Neuroimaging studies in patients with phobias have revealed alterations in amygdala reactivity and volumes. Here, we investigated the shape composition of the amygdalae to explore if patients with spider phobia show local morphological differences as compared to healthy controls. Magnetic resonance imaging data was analyzed from 20 female spider phobic patients and 20 age-matched healthy controls. Amygdala shape was quantified using a surface-based mesh modeling method (FIRST). Differences in amygdala topography were most prominently located over the basolateral and central nuclei of the left, but not right amygdala. These differences were further related to the severity of spider phobic symptoms and were independent of age, years of education or duration of illness. The present results point to focal amygdala distortions in spider phobic patients. Due to anomalies within the amygdala, spider phobia might be characterized by a deregulation in both an initial amplified fear response during exposure to spiders as well as a subsequent impaired down-regulation of the elicited fear response.