Fig. 1: LC4 VPNs pass looming location information to DNs that mediate forward or backward escape takeoffs.
From: Synaptic gradients transform object location to action
a, VPNs with retinotopically arranged dendrites in the lobula neuropil of the fly optic lobe have axon terminals in cell-type-specific optic glomeruli in the central brain. Dendrites of >50 postsynaptic neurons typically innervate each optic glomerulus. Inset: EM-based reconstructions (hemibrain connectome27) of 71 LC4 VPNs (blue), a single LC4 neuron (red) and LC4 postsynaptic partner, GF DN (black). VNC, ventral nerve cord; D, dorsal; L, lateral; glom., glomerulus. Scale bar, 20 μm. b, Confocal projections of GFP (green) expression in seven DNs innervating the LC4 glomerulus (red dashed line). Grey, brain neuropils. Images adapted from ref. 24, CC BY 4.0 (n = 4 brains for each DN). Scale bar, 50 μm. c, Synaptic connectivity from looming-sensitive VPN cell types onto seven DNs based on the hemibrain connectome. Arrow width is proportional to synapse number. Pie charts indicate proportion of a given DN’s inputs from each looming-sensitive VPN cell type. d, Forward–backward postural shifts in response to DN photostimulation; quantified as Δ[T2 leg angle], the change in angle between the middle jumping legs and COM. e, Δ[T2 leg angle] 75 ms after the onset of 50-ms photostimulation. Points, individual flies; error bars, s.d.; one-way analysis of variance (ANOVA), Dunnett’s test, ***P < 0.001, exact P values in Supplementary Table 1. f, Δ[T2 leg angle] time courses from machine-learning-tracked data; red shaded area, photostimulation period. g, Δ[T2 leg angle] for a subset of manually annotated flies. In f,g: lines, mean; shading, s.d. h, Takeoff direction is COM movement direction between onset of middle leg extension and takeoff. i, Polar histograms of optogenetically activated takeoff direction. Red line, circular mean; n, number of flies tested; \(\bar{R}\), mean vector length; P, Hodges–Ajne test for angular uniformity.
