In vivo imaging methods, particularly translocator protein positron emission tomography (TSPO-PET) and dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI), have advanced our understanding of glial activation and BBB permeability in conditions such as Alzheimer’s disease, Parkinson’s disease, epilepsy, multiple sclerosis, Huntington’s disease, schizophrenia, and depression. The gene discussed is TSPO; the disease is depressive disorder.