Fig. 4

Tracing VPM pathway with H129-ΔTK-tdT (a) Experiment time line for tracing VPM pathway with H129-ΔTK-tdT and the helper. b Schema of the simplified VPM-S1 circuit. The projection of the inhibitory interneurons at nRT was indicated by the dotted line. VPM, ventral posteromedial thalamic nucleus; nRT, nucleus of reticular thalamus; S1, primary somatosensory cortex; IV, V and VI, layer 4, 5 and 6 of the cortex. c–d Controls of the helper and H129-ΔTK-tdT alone. AAV-TK-GFP (c) or H129-ΔTK-tdT (d) was individually injected into the VMP of wild-type C57BL/6, and images were obtained at 21 (c) or 10 dpi (d), respectively. The injection sites are shown in the dotted boxes. e The starter neurons of H129-ΔTK-tdT transmission. AAV-TK-GFP and H129-ΔTK-tdT were injected into VPM of wild-type C57BL/6 mice at Day 1 and 22 sequentially. Brains were obtained at Day 25, and coronal brain slices were stained with anti-NeuN and anti-tdTomato antibodies. The magnified image of the injection site (e1) and nRT (e2) is shown, and the representative regions are further magnified (e3 and e4). The starter neurons, which expresses both tdTomato and GFP, are indicated with the white arrows. f–h Tracing the monosynaptic output of VPM. The animals were perfused at Day 32, and the coronal brain slices throughout the brains were observed. The representative tracing images of the S1 (f–h) in VPM circuit are shown. The cortical layers at S1 are determined according to NeuN staining and indicated by the dotted lines (h)