MAPT and Alzheimer disease: In fact, we have recently observed that in patients with AD the accumulation of phosphotau in a pretangle state does not induce changes in the dendrites of pyramidal neurons, whereas the presence of tau aggregates forming intraneuronal neurofibrillary tangles gives rise to a progressive dendritic atrophy and the loss of dendritic spines (synaptic disconnection) (Merino-Serrais P et al. in preparation).