GRM5 and Alzheimer disease: Regions with more baseline atrophy possessed higher concentrations of serotonin 5-HT6 and glutamate (mGluR5) receptors in HC (5-HT6: r = 0.45, P-valuespin-FDR = 0.004; mGluR5: r = 0.44, P-valuespin-FDR = 0.004), FHAD (5-HT6: r = 0.46, P-valuespin-FDR = 0.004; mGluR5: r = 0.48, P-valuespin-FDR = 0.004) and Alzheimer's disease (5-HT6: r = 0.35, P-valuespin-FDR = 0.004; mGluR5: r = 0.42, P-valuespin-FDR = 0.004).