Abstract
Time is of the essence in the execution of visually guided behavior in dynamic environments. We have been investigating how the visual system responds to unexpected changes of the image when a saccade is being planned. Performance of stop signal or double-step tasks can be explained as the outcome of a race between a process that produces the saccade and a process that interrupts the preparation. Neural correlates of dynamic target selection and these race processes have been identified in the frontal eye field and superior colliculus. The timecourse of these processes can provide useful leverage for understanding how early visual processing occurs.