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. Author manuscript; available in PMC: 2016 Jun 1.
Published in final edited form as: Curr Biol. 2015 May 7;25(11):1526–1534. doi: 10.1016/j.cub.2015.04.025

Figure 2. Loss of M-cells or spiral fiber neurons largely abolish short-latency escapes.

Figure 2

A. Top image: Representative escape behavior of a head-embedded larval zebrafish responding to a tap stimulus. Images were recorded every millisecond and here every 8th image is shown. The first image was taken at the time the tap stimulus hit the dish holding the larvae. The image marked with a star corresponds to the beginning of the escape response (8 ms latency). Bottom panel: Representative smoothed tail trace showing the angle of the last tail segment with respect to the vertical in response to a tap. The escape behavior consists of a sharp angle C-bend, followed by a counter turn in the opposite direction and subsequent swimming lasting hundreds of milliseconds. The dotted line shows the stimulus. The inset shows the first 300 ms after stimulus onset and the star indicates the start of the C-bend.

B–J. Results of M-cell ablations (B–D, n = 14 fish), spiral fiber (SF) neuron ablations (E–J, n = 13) and control ablations (H–J, n = 23) on the escape behavior in response to taps. B, E, H. Stack projections showing before (top image) and immediately after (B) or 24 hours after (E, H) two-photon laser-mediated bilateral ablations (bottom image). B. Et(fos:Gal4-VP16)s1181t; Tg(UAS:GCaMP-HS). E, H. Tg(-6.7FRhcrtR:gal4VP16); Tg(UAS:Kaede). Red dots mark the cells or location within the M-cell that were targeted for ablation. Green ovals in E mark the axon caps, which are no longer apparent 24 hours after ablations. High fluorescence cell debris can be observed in the post images. C, F, I. Escape probability as a function of latency of all escapes performed, mean +/- SEM, before ablations (black) and after (red). The dotted line at 13 ms demarcates short- (SL, ≦ 12 ms) and long-latency (LL, 13–25 ms) escapes. D, G, J. Probabilities of different types of responses as a function of all trials before (black) and after (red) ablations. Individual fish are displayed as semi-transparent dots and horizontal bars are the medians. Left: SL escapes; middle: LL escapes; right: overall responses (RE). M-cell: p = 0.013 pre vs. post (SL), 0.016 (LL) and 0.125 (RE); spiral fiber neuron: p = 2.4*10−4, 2.4*10−4, and 0.25; Control: p = 0.28, 0.20 and 1; Wilcoxon signed rank test.

K. Change in SL escape probability as a function of all trials (post-pre) based on the SL data plotted in D, G, J. Individual fish (grey circles), median (black line). M-cell vs. spiral fiber neurons: p = 0.11; M-cell vs. Control: p = 0.011; spiral fiber neurons vs. Control: p = 1.6*10−6, Wilcoxon rank sum test.

* denotes p < 0.05; NS not significant. Pictures are oriented rostral up; scale bars: 20 μm. Abbreviations: SF: spiral fiber; LS: short-latency; LL: long-latency; overall response. See also Figure S2.