MAPT and Alzheimer disease: We therefore hypothesized that, for the propagation model to be credible in human diseases, tau would need to be found at the synapse (at least in the disease state); if present at the synapse, the identification of tau species differentially present in pre- or post-synaptic elements, and in AD compared to controls, will test the further hypotheses that misfolded tau accumulates presynaptically before "release" into postsynaptic space, and that tau is mislocalized to the synapse in AD compared to normal neurons.