Fig. 2: Synaptic number gradients between LC4 and DNs transform a retinotopic map in the optic lobe to movement direction.
From: Synaptic gradients transform object location to action
a, Fly visual system (dorsal view). The A–P axis of the visual space is mapped onto the anatomical lateral–medial axis of the lobula neuropil. The outlined area is shown in b. b, Anterior and posterior visual inputs to LC4 neurons through two optic chiasms (OCHs). Images in a,b adapted from ref. 50, CC BY 4.0. c, DNp02 (red) and DNp11 (blue) dendrites receive input from LC4 neurons (grey) in the glomerulus formed by LC4 axon terminals. Shown are neuron skeletons (red and blue). Scale bar, 50 μm. d, LC4 dendrites in the lobula (lateral view) colour-coded according to the number of synapses their axons make onto DNp02 or DNp11. LC4–DNp02 and LC4–DNp11 synaptic gradients are antiparallel along the A–P axis of the visual space. Scale bar, 20 μm. All neurons in c,d are manually reconstructed from the EM FAFB dataset. e, Antiparallel A–P gradients are also seen in the hemibrain connectome. Dots, two-dimensional (2D) lobula projections of dendritic centroids for individual LC4 neurons in the lobula weighted in size and colour by the number of synapses made by their axons onto DNp02 and DNp11. Scale bars, 25 μm. f, Regression of LC4-DN synaptic weights as a function of LC4 dendrite centroid location; colour as in e. Linear fit line overlaid. Error bands, s.e.m. g, Hemibrain connectome reconstruction of LC4 dendrites coloured on the basis of a normalized (−1 to 1) number of synapses each LC4 neuron forms with DNp02 and DNp11. Some anterior lobula dendrites exceed the EM volume and are not fully reconstructed. h, Correlation between the number of synapses each LC4 neuron (n = 71) makes with DNp02 and DNp11. rs, Spearman’s rank correlation coefficient. A, anterior; P, posterior; D, dorsal; L, lateral. Error band, s.e.m.
