Fig. 4. Synaptic gradients are a general property of VPN output organization.
a,b, Connectivity-based k-means clustering of individual neurons within 20 VPN cell types (see Methods). Lateral views of VPN dendrites in the lobula (hemibrain connectome reconstructions). Individual cells within one VPN cell type are coloured by their cluster identity. Colours do not correspond between VPN types. Most VPNs exhibit distinct spatial separation (examples in a), but in some cases (LC12 and LC17 in b) there is no clear separation. Scale bars, 20 μm. c, Differential connectivity (number of synapses) across individual neurons within one VPN cell type. Measured for 20 VPN cell types and their postsynaptic partners that make at least 50 synapses total. Coefficients of variation in synapse number are averaged across all postsynaptic partners per VPN cell type. d, Matrix of pairwise correlations in synaptic connectivity between LC4 and its top 25 postsynaptic partners; ordered by hierarchical clustering as indicated by coloured side bars; rs, Spearman’s rank correlation coefficient. e, Topographic map of input centroids, weighted by number of synapses, for top 25 postsynaptic partners of LC4. Dark grey shading, lobula 2D projection; small open circles, centroids of 71 individual LC4 dendrites; coloured circles, weighted input centroids; solid blue line, median separation line; dashed blue line, projection line (see Methods). Red squares indicate centroids of DNp02 and DNp11. Scale bar, 25 μm. f,g, Similar analysis as in d,e, but for LPLC2. Red squares, centroids of neurons PVLP071 and PVLP076. Scale bar, 25 μm. h, Representative examples of synaptic gradients reflecting A–P and D–V axes of dendritic maps in multiple VPN cell types. syn., synapses. Scale bars, 25 μm (images 1 and 6–8) and 30 μm (images 2–5). A, anterior; P, posterior; D, dorsal; V, ventral. Error bands, s.e.m. See legend for Fig. 2c,d.