Fig. 7. Laminar and tangential distribution of long-range V1 inputs.

a Case MK405. Image of a single tangential section through V1 L2/3–4C stained for CO (Left) after being imaged for mCherry and GFP fluorescence (Right). The merged channel shows plenty of GFP-labeled V1 input cells (green) in L2/3, 4A–4C away from the injection sites (arrows). The locations of the injection sites were determined in more superficial sections where the CO discoloration was more visible than in the indicated section. The region inside the boxes is shown at higher magnification in (b, c). Other conventions are as in Fig. 2. Scale bar: 500 µm. b, c GFP-labeled V1 input cells in L2/3 (b) and L4B (c), shown under GFP (Left) or mCherry (Middle) fluorescence, and merged (Right). Scale bars: 50 µm. Results in (a–c) are representative of the V1 GFP label in three independent TRIO experiments. d Percent and number of long-range V1 input cells across layers for each of the three cases. e Average percent ± s.e.m. of V1 input cells across V1 layers for the population. f Tangential spread of V1 input cells for each case (GFP-labeled cells within 400 µm of each V1 injection site were omitted from the counts). g Average percent of cortical inputs arising from V2 vs. V1 for the population (n = 20,369 cells in 3 independent animals). Error bars: s.e.m. Results in (a–c) are representative of injection sites made in three independent cases with similar results.