Fig. 5

Single-pulse MLR stimulations gradually recruit a subset of V2a RSNs.

a, Distribution and density of RSNs in the V2a neuronal population. a1, Example image of the hindbrain of 5-dpf Tg(vsx2:Kaede) larval zebrafish after photoconverting Kaede protein in the rostral spinal cord. Scale bar, 50 µm. a2, Mean proportion of V2a RSNs (4 fish). b1, Schematic illustration of the experiments investigating V2a neuron recruitment in response to MLR stimulation in paralyzed Tg(vsx2:GAL4;UAS:GCaMP6s) transgenic 6-dpf larval zebrafish. b2, Typical calcium traces of reliably recruited V2a neurons in the different anatomical regions investigated (top, colored traces: vP, dP, vRP, dRP and medulla). The gray traces at the bottom represent neurons not labeled as reliably recruited. c, The recruitment of V2a neurons fell into three groups: reliably recruited (the color corresponds to reliably recruited neurons in a given anatomical area); unreliably recruited (gray); and not recruited (black) (5 fish, total 1,781 neurons; vP: 42 neurons; dP: 96 neurons; vRP: 88 neurons; dRP: 475 neurons; medulla: 1,080 neurons). d, Proportions of reliably recruited V2a neurons (mean ± s.d.) responding at each MLR stimulation intensity (proportions are relative to the numbers of V2a neurons in each anatomical group defined in b). e, Distribution of calcium transient rising slopes in reliably recruited neurons. The line is the median value (median ± s.d., 5 fish; vP: 18 neurons, 76 events, 64.4 ± 67.6 ΔF/F · s⁻¹; dP: 29 neurons, 87 events, 23.4 ± 20.2 ΔF/F · s⁻¹; vRP: 44 neurons, 177 events, 30.6 ± 43.3 ΔF/F · s⁻¹; dRP: 100 neurons, 326 events, 27.1 ± 30.7 ΔF/F · s⁻¹; medulla: 183 neurons, 583 events, 24 ± 27.3 ΔF/F · s⁻¹; two-sided Kruskal–Wallis test, χ² = 141.68, P < 0.001. Wilcoxon pairwise comparisons: vP versus dP: P < 0.05; vP versus vRP: P < 0.01; vP versus dRP: P < 0.01; vP versus medulla: P < 0.001; dP versus vRP: P = 1.0; dP versus dRP: P = 1.0; dP versus medulla: P = 1.0; vRP versus dRP: P = 1.0; vRP versus medulla: P = 1.0; dRP versus medulla: P = 1.0). P values were adjusted using the Bonferroni method. f, Location of reliably recruited V2a neurons (dot size scaled with the median of all computed rising slopes for each neuron).

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