MAPT and Brain atrophy: In addition to PET-Aβ imaging, brain atrophy assessed by magnetic resonance imaging (MRI), cognitive decline assessed by neuropsychological scores (episodic memory [EM] and the Preclinical Alzheimer’s Cognitive Composite [PACC]), and CSF measurements of Aβ1-42, total tau (T-tau), and tau phosphorylated at threonine 181 (P-tau181P) all reflect the natural history of AD in the three major stages [6].