Fig. 4 a Celloidin‑embedded gallocyanin‑stained 420‑μm‑thick horizontal brainstem section of a 85‑year‑old female case. b Axial 7 T post‑mortem MRI (Siemens) after 3 months of formalin fixation of the complete brain—with a 3D gradient‑echo acquisition (TE 8 ms, TR 12 ms, 0.6 mm thickness, 0.3 mm in plane resolution)—at corresponding horizontal level. c Merged a and b with semitrans parent c on the bottom of the stack. Arrows in a and c point to the lateral angle of the aqueduct. Arrowheads in a point to the locus coeruleus. Scalebar in a and c subdivided into