We also found that synaptic density in the medial temporal lobe of CI individuals and HCs was positively associated with global cortical mGluR5 availability (r = 0.609, p = 0.004) and regional mGluR5 availability in the frontal (r = 0.576, p = 0.008), lateral parietal (r = 0.488, p = 0.029), lateral temporal (r = 0.671, p = 0.001), and occipital lobes (r = 0.570, p = 0.009) and precuneus (r = 0.461, p = 0.041) and posterior cingulate cortex (r = 0.617, p = 0.004), and these associations were independent of global amyloid deposition. The gene discussed is GRM5; the disease is amyloidosis.