AQP4 and Alzheimer disease: Here we study the glymphatic system using MRI, the clearance of parenchymal tau using intracerebral injections and CSF sampling, and the modulation of AQP4 function, in a mouse model that develops tau NFT pathology (Ramsden et al., 2005) similar to that seen in neurodegenerative diseases such as Alzheimer’s disease (Braak and Braak, 1995).