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. 2021 Feb 3;15:636683. doi: 10.3389/fnana.2021.636683

Figure 1.

Figure 1

Overview of TL-tectum circuit and PyrN connectivity. (A) Dorsal view fluorescence image of a Tg(HuC:lynTagRFP-t) larval brain in which all axon tracts and neuropil areas are fluorescently labeled, with superimposed schematic of the brain regions examined in this study. Connectivity of TL-tectum circuitry: ipsilateral TL forms an axonal projection terminating in the SM layer of the tectal neuropil. The contralateral retina forms an axonal projection terminating in tectal layers distinct from SM. (B) Higher magnification side view of the midbrain of brain volume in (A). Overlayed schematic depicts the relative laminar positions of retinal input layers relative to SM, other non-retinorecipient neuropil layers, and PyrN stratification pattern. (C) Putative connectivity of id2b:gal4 positive PyrNs. Based on laminar position of dendrites PyrNs most likely receive TL-derived inputs on their SM dendrite and retinal inputs on their SFGS dendrite. PyrN axon stratifies within the SGC layer.