Figure 2.

Visual sensitivity is selectively modulated by exposure to water flow. A, Flow chamber for testing activity and sensory thresholds. Optomotor stimuli are projected onto the diffuser using a mirror. Leads attached to grids enable electric stimuli. LED mounted above the chamber for visible illumination and flash responses. To test responsiveness, larvae were left in the chamber for 25 min before recording baselines, exposed to a 60 s flow stimulus at 30 min, and retested 3 min after flow. B, C, Responsiveness was measured to an electric stimulus (B) (n = 7 × 20) and a light flash stimulus (C) (n = 9 × 20). D, To test touch responsiveness, larvae expressing ChR2 in the trigeminal ganglion were exposed to five brief blue light pulses before and after water flow (open circles; n = 10 larvae) or before and after an equivalent delay without water flow (“no flow”) to control for habituation (filled circles; n = 11 larvae). E, Average orientation during the first 10 s of water flow. Orientation is the offset (0–180°) from the direction opposite to flow. Larvae orient more quickly to a second exposure to water flow, 3 min after the termination of the first exposure (open circles) than to the initial exposure (filled circles). F, Proportion of larvae in orientation bins (30 ° each) relative to flow direction, 5 s after flow stimulus starts, for first exposure (top) and second exposure (bottom). *p < 0.05 compared with the same orientation at first flow exposure. G, Rate of orienting during the OMR. The proportion of larvae (n = 19 × 20) oriented in the quadrant matching the direction of visual flow was measured throughout stimulus presentation and rate of increase calculated in baseline state (filled circles) or after exposure to flow (open circles). *p < 0.001. H, Turn bias during the OMR. Larvae (n = 23 × 20) were tested in baseline state (filled circles) and then after flow (open circles). *p < 0.05. Graphs show mean and SEM.