Express-Saccades of the Monkey: A New Type of Visually Guided Rapid Eye Movements After Extremely Short Reaction Times

Monkeys are trained to fixate a stationary small central spot and to saccade to a peripheral target. The saccadic reaction times depend on the temporal sequence of fixation point off set and target on set and form a spectrum between 60 and 400 ms containing at least 4 peaks. If the fixation point is turned off before the peripheral target appears (gap duration in the order of 200 ms) a rather narrow (± 3 ms) distribution of reaction times is obtained with a peak at 75 ms (express-saccades). The exact mean value of the reaction times depends on the amount of daily training (and on the physical parameters of the target). Reaction times of the regular saccades may be shortened by as much as 200 ms by daily exercise those of the express-saccades by about 20 ms.