(a) The reconstruction and quantification of the terminal arborizations of the 3 reconstructed DA neurons shown in Fig. 1h. The bottom left panel shows the detailed distribution of the terminal arborizations in the medial shell of the nucleus accumbens (NAcShMed; A: anterior; P: posterior; M: medial; L: lateral). Fiber densities of each arborization were computed over anterior-posterior direction of NAcShMed. The top left panel shows the projection of an fMOST image stack (240 × 240 × 100 µm3) of the boxed region in the bottom left panel. The top right panel demonstrates the serial reconstruction of the arborizations in the boxed region (60 × 60 µm2) in the top left panel. Image stacks of both fMOST GFP signal (upper) or reconstruction overlay (lower), with increasing thickness of 1 µm, 10 µm, 50 µm, and 100 µm are shown. (b) The axon arborizations of 3 neurons shown in (a) have a layered-organization with partial overlapping in NAcShMed. (c, d) The alpha-shapes of DA neurons (c) 1–3 and (d) 5–7. An alpha-shape encompassing the reconstructed points was computed using the MATLAB generic function with the parameter alpha equal to critical alpha, which ensures that the alpha-shape encloses one region. The volume and critical alpha were indicated at the left. (e) The fiber density of DA neurons 5–7 in the dorsal striatum. The surface boundaries of the nucleus accumbens (NAc, green) and dorsal striatum (DS, yellow) were extracted from the Allen Mouse Common Coordinate Framework version 3 (CCFv3), manually adjusted against PI stained coronal image slices, and are displayed from the dorsal-ventral axial angle. Scale bars, 50 µm (a, top left), 10 µm (a, top right), 250 µm (a, bottom left), and 500 µm (e).