Asymmetries in saccadic latencies during interrupted ocular pursuit

Smooth pursuit eye movements can be interrupted and resumed at a later stage, eg, when a concurrent task requires visual sampling from elsewhere. Here we address whether and how interruptive saccades are affected by pursuit movements. Our participants pursued an object which moved horizontally in a sinusoidal pattern (frequency: 0.25 Hz, amplitude: 4 deg. visual angle). During this, discrimination targets appeared at 10 deg. eccentricity, to the left or right of the center. They were timed so that they appeared for 1 second while the pursuit object moved either toward or away from the discrimination target's position. Saccade reaction times were earlier when the discrimination targets appeared in a position that the tracking object was moving towards. Interestingly, saccade RTs back to the pursuit object were shorter when the object moved away from the discrimination target. We conclude that interruptions of pursuit movements lead to asymmetries in saccade generation. These asymmetries could have been caused by biases in attention along the predicted pursuit path