Predicted sequence of cortical tau and amyloid-beta deposition in Alzheimer disease spectrum

Abstract

We investigated sequential order between tau and amyloid-beta (Abeta) deposition in Alzheimer disease spectrum using a conditional probability method. Two hundred twenty participants underwent (18)F-flortaucipir and (18)F-florbetaben positron emission tomography scans and neuropsychological tests. The presence of tau and Abeta in each region and impairment in each cognitive domain were determined by Z-score cutoffs. By comparing pairs of conditional probabilities, the sequential order of tau and Abeta deposition were determined. Probability for the presence of tau in the entorhinal cortex was higher than that of Abeta in all cortical regions, and in the medial temporal cortices, probability for the presence of tau was higher than that of Abeta. Conversely, in the remaining neocortex above the inferior temporal cortex, probability for the presence of Abeta was always higher than that of tau. Tau pathology in the entorhinal cortex may appear earlier than neocortical Abeta and may spread in the absence of Abeta within the neighboring medial temporal regions. However, Abeta may be required for massive tau deposition in the distant cortical areas.