Sensitivity of express saccades to the expected value of the target.

Express saccades, a distinct fast mode of visually guided saccades, are probably underpinned by a specific pathway that is at least partially different from the one underlying regular saccades. Whether and how this pathway deals with information on the subjective value of a saccade target is unknown. We studied the influence of varying reward expectancies and compared it with the impact of a temporal gap between the disappearance of the fixation dot and the appearance of the target on the visually guided saccades of two rhesus macaques (). We found that increasing reward expectancy increased the probability and decreased the reaction time of express saccades. The latter influence was stronger in the later parts of the reaction time distribution of express saccades, satisfactorily captured by a linear shift model of change in the saccadic reaction time distribution. Although different in strength, increasing reward expectancy and inserting a temporal gap resulted in similar effects on saccadic reaction times, suggesting that these two factors summon the same mechanism to facilitate saccadic reaction times. Express saccades are the fastest visually driven way of shifting gaze to targets of interest. We examined whether the pathway underlying these saccades has access to information on the value of saccade targets. We found that not only regular saccades but also express saccades occur earlier in case of higher expectations of reward. Yet, the sensitivity of express saccades to reward decreases linearly when approaching the earliest possible reaction time.