Variability of response latency in single cells. The latency tuning curves of many cells showed differing response variability, depending on the direction of movement, as depicted in this example from unit 1 in experiment 1. (A) In this example, the typical W-shaped tuning curve for absolute latencies showed increased variability for downward movements (negative velocities). For upward movements absolute latencies were more precise. (B) This difference in variability between downward and upward movements was retained in the tuning curve for relative latency. In addition, shallow velocity tuning was preserved for upward movements (positive velocities). (C) Raster plot of the same cell showing the spike responses to all stimulus presentations with velocity -6 m/s and +6 m/s. The randomly presented stimuli were sorted for this diagram. Presentations 1 to 60 indicate all downward stimuli with -6 m/s velocity, presentations 61 to 120 all upward stimuli with +6 m/s velocity. The responses to upward movement show more precise timing than responses to downward movement.