Fig. 2

PyrNs respond to gradual changes in display luminance. A Overview of expression pattern in a 6 dpf id2b:gal4,uas:egfp,HuC:lynTagRFP-t larva. id2b-positive neurons are labeled in cyan, while axon tracts and neuropil are labeled in red. Upper right: reconstructions of the three neuron types labeled in the id2b:gal4 transgenic. Lower right: region of analysis that includes the deep tectal neuropil and shallow SPV. B Maximum projection whole-brain image of a 7dpf id2b:gal4,uas:gcamp6s larva with a single mTomato-labeled PyrN (red arrowhead). C Magnified view of boxed region in B containing a mTomato-labeled PyrN. D 40° rotated view around X-axis of boxed region in B. Note three distinct neurite stratifications in SM, SFGS, and SGC layers. E Standard deviation (StDev) projection image of a multiphoton timeseries acquired from region indicated in B during presentation of 10s ramp stimulus. Pixels with higher values correspond to regions that underwent large variations in fluorescence intensity during recording interval. Red arrowhead indicates mTomato labeled PyrN in B–D. F Ramp-evoked responses in neurons labeled 1–4 in E during presentation of 10s and 30s ramp stimuli. Red trace corresponds to the mTomato labeled PyrN in B–E. Note that all four neurons exhibit strong cycle locked responses that peak near the minimum stimulus light intensity. G Output of linear SVM classifier run on data acquired from 127 PyrNs in 6 larvae during presentation of 10s ramp stimulus. Note ON, OFF, and DUAL responses and a subset of neurons that did not respond to visual stimulation. H Confusion matrix demonstrating SVM performance compared to investigator-determined “true” classification. I Average responses to 10s ramp stimulus recorded from 100 active PyrNs in G classified by the linear SVM classifier as ON, OFF, or DUAL. Fourth panel depicts merged overlay of three response types. Note sequential activation of DUAL, ON, and OFF PyrNs during each cycle of the luminance ramp. Scale bar, 50μm in A, 75μm in B, 30μm in C–D, and 25μm in E. TL Torus longitudinalis, SPV stratum periventriculare