GRIN1 and Alzheimer disease: Accordingly, levels of GluN1, GluN2B, and GluN2A are reduced in extracts from AD-susceptible regions such as the hippocampus, entorhinal cortex, frontal cortex, or cingulate cortex from individuals with AD with respect to controls [132,133,138,144], but no changes are reported in less susceptible regions, such as the occipital cortex or the caudate [144].