Supplementary Figure 4: Inter-areal SBEM and neurite traceability.

(a) Complete block-face SEM image (top, 440 nm pixel size, 4 kV, 150 pA, 0.0097 e^-/nm²) of a BROPA brain and a higher-magnification view of the region of interest (bottom). The red rectangle shows the approximate extent of a continuous SBEM stack. The normal of the stack images is along the long axis of the rectangle. (b) From the left: surface view of aligned stack; manually identified neuronal (blue) and glial (red) nuclei; neurites emerging from 381 randomly-selected nuclei. 6 of 381 neurons (3 each in cortex and striatum) together with 100 randomly selected external-capsule axons. Note that one of them veers into cortex. (c) Single cortical cell with dendrites (thin blue lines), the initial segment and an ascending collateral (thick red, both unmyelinated), and the descending axon (thin blue line) with nodes of Ranvier (red). Scale bars are 1 mm in a (top), 500 µm in a (bottom), and 40 µm in c.