Fig. 11. (A) (Top) Averaged (n=8) vector plots based on particle motions caused by the vortex stimulus passing the fish laterally. Particle motions were recorded during the reproducible bursts marked by the first vertical gray bar and during the following period of decreased neural activity marked by the second vertical gray bar. (Middle) Raster plots of the responses to the vortex stimulus and (bottom) peri-stimulus–time histograms (PSTH; bin width 20 ms) based on these raster plots. Note that the flow pattern during the bursts marked by the first vertical gray bar was similar to the flow pattern that occurred after the bursts (second vertical gray bar). (B) (Top) Raster plot of the third trial shown in A. (Bottom) discharge rate (spikes per 40 ms, black trace) calculated for that trial, and local water velocities (red trace) obtained from the interrogation window indicated by the red vector in A. This interrogation window is at the position of the neuromast. The blue trace shows the first derivative of the velocity data (i.e. water acceleration). Note that during the late bursts, small rhythmic fluctuations occurred in both local water velocity and local water acceleration. (C) (Top) Fast Fourier transformations (FFTs) of the discharge rate (trial 3 in A) and the corresponding FFTs of the velocity (red; middle) and acceleration traces (blue; bottom) shown in B. Note that both neural activity and water acceleration have peaks at 3 and 8 Hz.