Fig. 3.

Number of remaining teeth and correlation with tau lesions in the locus coeruleus and hippocampal region. A) Anatomical volume of interest of locus coeruleus (LC-VOI) on normalized PET and MRI images of HCs and AD. B) Group comparison of tau PET SUVR values in LC-VOI between HCs and AD groups. The p value was estimated by Mann-Whitney U-test. Open and filled circles indicate HCs and AD-spectrum patients, respectively. C) Correlations of tau PET SUVR values in LC-VOI and the number of remaining teeth in HC and AD groups; r and p values were assessed by Spearman’s rank correlation test. D) T-maps illustrate that tau PET tracer accumulation was increased in the hippocampal region in association with an increase to LC in AD (uncorrected, p < 0.001). The hippocampus VOI (red) is also overlaid in the right brain image. The cluster size threshold was set to zero according to the size of the LC-VOI. The statistical map was overlaid on the MNI brain. AD, Alzheimer’s disease; HCs, healthy controls; LC, locus coeruleus; MNI, Montreal Neurological Institute; PET, positron emission tomography; SUVR, standard uptake value ratio; VOI, volume of interest.