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Fig. 3 Neuronal Responses in the Pretectum Are Anatomically Lateralized and Direction Selective for Glider Stimuli (A) Whole-brain anatomical map from a reference brain (constructed from a confocal stack of Tg(elavl3:GCaMP6f) 7 dpf larva), on which all subsequent ROI selectivity maps were overlaid. Brain structures referred to in the text are highlighted (approximate locations). OT, Optic Tectum; Pt, Pretectum; Ce, Cerebellum; Hb, Hindbrain. (B) Schematic of two-photon imaging setup in which the larva was head-embedded in agarose but free to move its tail. We presented visual motion stimuli from below, and the behavior could be tracked while imaging the neural activity. (C) Whole-brain direction selectivity map moving sine gratings, revealing left preferring (green) and right preferring (magenta) regions (30,778 ROIs from 11 fish). (D) Whole-brain direction selectivity maps for two-point glider stimuli. (E) Pretectum direction selectivity maps for negative two-point glider stimuli. Direction selectivity in the ventral (dorsal) pretectum was opposite (matched) to the orientation of positive two-point glider stimuli (559 ROIs from 11 fish). (F) Pretectum direction selectivity maps comparing all stimuli driving leftward turning (green) to those driving rightward turning (red). Direction selectivity in the pretectum was lateralized in a manner that matched the direction of the turning behavior. For each set of maps, we show coronal (center of triplet), transverse (top of triplet), and right sagittal projections (right of triplet). A indicates the anterior-posterior axis, V the ventral-dorsal axis, and L the left-right axis. Scale bars represent 0.1 mm in (C), (D), and (B) and 0.05 mm in (E) and (F). (G) Mean z-scored fluorescence responses of ROIs in the left (N = 840 ROIs) versus right pretectum (N = 991 ROIs). Each mean was direction selective for each directional pair of stimuli, and directional preferences matched the behavioral turning directions. Shaded error bars represent SEM. Green and red colored dots signify visual stimuli driving left turning and right turning, respectively. Horizontal dashed lines mark the peak average responses during the uncorrelated stimulus presentation. Asterisks indicate that all comparisons were significant at the p = 0.01 level (Wilcoxon test). See also Figure S2.