Fig. 1

Optogenetic Mapping of the Tectum Reveals a Motor Map (A) Schematic drawing of the optogenetic setup. Zebrafish larvae (5–7 dpf; Gal4s1013t; UAS:ChR2-mCherry; UAS:paGFP) are head-embedded in agarose, whereas the tail is free to move. A 50-μm optic fiber is used to stimulate ChR2-expressing tectal neurons at 473 nm while the behavior is recorded at 344 fps. (B) Optogenetic activation of tectal neurons triggers behavior. Different elicited behavioral outcomes are shown as time projections along with the corresponding tail kinematics. Fish were stimulated for 3 s (blue background). (C) Characterization of the behavior. DBSCAN (density-based spatial clustering of applications with noise) clustering of the mean bout angle and maximum amplitude of the first bouts triggered in each stimulation reveal two kinematically distinct behavioral outcomes: approaches and escapes. On each axis, the probability density functions are displayed for the two behaviors. (D) Average of maximum amplitudes and mean bout angles for the different clusters of behavior. (E) Response probabilities for ChR2-expressing and non-expressing fish (∗∗p = 1.3 × 10−6). (F) Fish co-expressing ChR2 (red) and paGFP were used to mark the stimulated region by photoconverted paGFP (white) after photostimulation with ChR2. (G) The mean bout angle increases with stimulations along the anterior-posterior axis (n = 20 fish), estimated by the center of gravity of photoactivated neurons. (H) Influence of the initial eye position (i.e.p.) on the induced behavior. Shown is a time projection of the optogenetically induced behavior in fish with the eyes freed. The colored arrows indicate the left or right movements of the tail depending on the initial eye position (white arrowheads). Right: traces of eye and tail angles for the time projections, highlighting the stimulation (blue) and the initial position of the contralateral eye (dashed red line). (I) Quantification of the mean bout angle in relation to the initial eye position. For all induced bouts (n = 8 fish, ∗∗p = 7.4e−4), red points indicate nasal and blue point temporal eye positions. The probability density histograms show a bimodal distribution for the eye position, resulting in a shift in the distribution of tail angles. Right: the shift in mean bout angle depending on the eye position for eight fish. The scale bar represents 50 μm. Data are presented as mean ± SEM. See also Figures S1 and S2.