MAPT and Alzheimer disease: However, given that in human brain‐derived synaptosomes, a recent study observed that phospho‐tau is increased in Aβ‐positive synaptosomes in early AD (Bilousova et al., 2016), it is possible that at the time point studied here, synapse loss had already reached its maximum level and thus it was too late to see the potentially early effects of human tau expression.