TSPO and Alzheimer disease: In disease with gliosis, the regions most affected typically have the most elevated TSPO VT, such as the hippocampus in Alzheimer disease, the cortico-striatal-thalamic circuit involving orbitofrontal cortex in obsessive compulsive disorder, or the focal injury of a stroke. Elevations in TSPO VT in other brain regions, such as the anterior cingulate cortex and hippocampus included in the initial grouping of regions compared, likely represent a lower level of gliosis (compared with the ventral striatum and dorsal putamen).