Figure 1. Visual layer boundaries of mouse superior colliculus (SC).

A. A schematic shows the labeling of the contralateral superficial part of the SC after cholera toxin b subunit (CTB) injection into one eye (magenta). Vibratome sections were subsequently prepared at ~P22 and immunostained. B. A section stained with anti-myelin basic protein (MBP, green) and CTB. The dashed line delineates the pial surface. A boundary between stratum griseum superficiale (SGS) and stratum opticum (SO) is delineated by the boundary between intense labeling of myelinated fibers (B1) and dense labeling of CTB (B2). From the merged image (B3), a higher magnification of the boxed area is shown (B4). The question mark indicates the inability to locate the boundary between SO and stratum griseum intermediale (SGI) based on MBP labeling. C. A section stained with anti-choline acetyltransferase (ChAT, green). The dashed line delineates the pial surface. A boundary between SO and SGI is delineated by the boundary between intense labeling of ChAT-positive fibers (C1) and the deepest retinal fiber labeled by CTB (C2). From the merged image (C3), a higher magnification of the boxed area is shown (C4). The question mark indicates the inability to locate the boundary between SGS and SO based on ChAT labeling. D. Schematic of layer distinctions based on CTB labeling (magenta), MBP staining (green) and ChAT staining (yellow). The dashed lines and question marks indicate the inability to locate certain boundaries. Scale bar: 200 μm (B1-B3 and C1-C3), 100 μm (B4 and C4).