In addition, numerous studies have reported enhanced TSPO PET signals in various brain regions in subjects with different neurodegenerative diseases, such as PD, AD, and HD; as well as neurodevelopmental disorders, such as schizophrenia and autism; psychiatric disorders, such as major depressive disorder; and brain injuries (for example, reviewed in [49,50,51]). This evidence concerns the gene TSPO and Alzheimer disease.