Figure 3.

Two scenarios whereby saccade plans may incorporate new visual information. Traces represent the activity of saccade-related neuronal populations. Each color represents activity associated with a different saccade direction. Activity rises progressively, and when it reaches threshold, a saccade is triggered and a new motor plan is initiated. Here, all plans have the same build-up rate. The circuit detects a new stimulus (red flash) at a time αQ relative to the onset of the ongoing plan (black trace). (a,b) A serial programming scenario. Saccade plans are produced every Q ms and cannot be interrupted. After stimulus detection, the next saccade may be to an unrelated location ((a) blue trace) or toward the flash ((b) red trace), in which case its latency is RT₁ ms from the time of detection. (c,d) A concurrent-programming scenario. After stimulus detection, the ongoing plan (black trace) is halted for q ms and a second plan, toward the stimulus (red trace), starts rising. After the interruption, either the second plan is canceled (c), or the first one is (d), in which case a saccade to the flash is made after RT₂ ms from the time of detection.