Fig. 1.

Neurobiological evidence implicates the amygdala as well as serotonergic (serotonin, 5-HT) signaling via postsynaptic 5-HT_2AR as essential substrates of anxiety behaviors. However, the functional relationship between these substrates is unclear. We hypothesized that a low-fear behavioral phenotype due to bilateral lesion of the amygdala is associated with significant changes in 5-HT_2AR expression. Thus, we used [¹⁸F]altanserin PET referenced to radioligand plasma levels and corrected for partial volume effects to quantify the spatial distribution of 5-HT_2AR BP_P in a rare patient with Urbach–Wiethe disease and selective bilateral amygdala calcification damage relative to 10 healthy control subjects.