Human brain tissue
Five human autopsy brains of male and female patients without any neuropathological changes (age 61–77 years; post mortem interval: 12–72 h) were fixed in an aqueous solution of formaldehyde for three weeks. Blocks of the parietal neocortex were embedded in paraffin and microtomed at 12 μm thickness. Sections were stained with aldehydefuchsin Darrow-red to confirm the absence of neuropathological alterations. All procedures were conducted in accordance with the Declaration of Helsinki and approved by the ethics committee of the University of Bonn Medical Center.