Evidence for high-velocity smooth pursuit in the trained cat.

It is generally accepted that in cats smooth pursuit velocity of the eye never exceeds a few degrees per second. This is in contrast with observations in primates, where smooth pursuit velocity can reach values as high as 100 degrees/s. Cats were trained to fixate and pursue spots of light appearing on a translucent screen. Spots were moved in the horizontal and vertical planes at different constant velocities up to 80%. Eye position was recorded with the scleral search coil technique. Naive cats did not pursue moving targets with high efficiency. Smooth eye movement velocity saturated at 5 degrees/s. After a few days of training, smooth-pursuit eye velocity increased with target velocity and saturated at 25 degrees/s on average. However, velocities twice as high have been observed frequently. When the target was unexpectedly extinguished, smooth eye movement velocity dropped to values close to 0 degree/s in approximately 350 ms. After a short training period (usually 5 times the same target presentation), the eye continued to move smoothly until the target reappeared. These data suggest that smooth pursuit eye movements of the cat are qualitatively similar to those of primates, but reach lower velocities and are more variable in their characteristics.