Time course of a repetition effect on saccadic reaction time in non-human primates.

Repeated training in a stimulus response task can lead to adaptive changes in the resulting behavior. Using a simple saccade task, we investigated the effect that the location of the target in the preceding trial had on the saccadic reaction time (SRT) of the current trial. To determine the time course of this effect, we varied the intertrial interval (ITI). Finally, we examined the pretarget discharge of single neurons in the intermediate layers of the superior colliculus (SC) during the task. Our data reveal that monkeys have a robust repetition effect in which there was an overall decrease in SRT and increase in SC pretarget activity when the target of the previous saccade was in the same location as that of the current trial. Additionally, we have shown a robust time course of this repetition effect, revealing that it exists for only a limited amount of time.