Fig. 4. Response of V1 neurone to repetitive stimulation of the lateral ocelli, showing that a switch in illumination from right to left ocellus generates a phase locked spike in V1, whose jitter increases over successive repetitions. (A) Responses averaged over 29 stimulus trials in a single animal; black line, peristimulus spike time histogram (10 ms bins); grey trace, instantaneous firing rate, as described in Materials and methods. (B) Raster plot of spikes recorded in 20 of the trials. (C) Time course of ocellar stimulation; LED intensity difference=(left LED output-right LED output); I_max, max LED output.