Importantly, these authors reported that the intensity of microglial activation, indexed by the second-generation 18-kDa translocator protein (TSPO) radioligand [18F]BRIII, within the hippocampus, was positively correlated with the severity of depression, indexed by the Beck Depression Inventory, while there was also a positive correlation between the hippocampal [18F]BRIII distribution volume ratio and the strength of hippocampal FC with prefrontal, parietal and occipital cortices [224]. This evidence concerns the gene TSPO and major depressive disorder.