Previous studies have revealed significant reductions in mGluR5 within the hippocampus in individuals with MCI due to AD or mild AD dementia via [18F]3‐Fluoro‐5‐[(pyridin‐3‐yl)ethynyl]benzonitrile ([18F]FPEB) and [18F]PSS232).21, 22, 23. This evidence concerns the gene GRM5 and Alzheimer disease.