Figure 18

The optic neuropils. A: overview (photomontage, confocal laser scan microscopy), vibratome section showing synapsin immunoreactivity (SYN; green in the inset), plus the nuclear marker (NUC; blue in the inset only; Apotome structured illumination technique). The three retinotopic neuropils from distal to proximal are the lamina (La), medulla (Me), Lobula (Lo) which is associated with an additional proximal lobula neuropil (LoP). The inset shows that the optic neuropils are surrounded by a cortex of neuronal somata. The boxed area is shown in E in a higher magnification. B: same specimen as A; maximum projection of several confocal sections to show the plexiform layer of the lamina. C, D: Triple labeling for synapsin immunoreactivity (SYN; red), RFamide-like immunoreactivity (RF; green), plus the nuclear marker (NUC) shown in conventional fluorescence combined with the Apotome structured illumination technique. In these tangential sections of the medulla, a regular arrangement of the labeled profiles signifies the ordered, retinotopic organization of this neuropil. E: higher magnification of the boxed area in A. In this image, contrast and brightness levels were artificially elevated, so that unspecific background staining reveals the presence of the inner optic chiasm, a cross-over of the fibers that connect the medulla and the lobula (enclosed between the arrows).