Figure 1 Feedback mechanisms of synaptic Aβ and tau in the progress of Alzheimer’s disease. Soluble oligomeric Aβ is the primary cause of synaptic dysfunction, whereas synaptic tau is the mediator in the progress. They locate in the synapse and work with receptors, synaptic proteins, and mitochondria to cause synaptic dysfunction, and ultimately lead to cognitive deficits. During the pathogenesis of AD, this is the early event, which occurs long before the formation of neurofibrillary tangles and senile plaques.