MAPT and Alzheimer disease: With respect to co-occurence of tau in AD/PART and aSyn in PD, the opportunity for the two proteins to be deposited in the same anatomical region occurs first in the brainstem, in particular the locus coeruelus, in early stages of disease, indicated as subcortical stages of neurofibrillary tangle pathology by Braak and colleagues [100] (Fig. 4).