Abstract
PURPOSE. Prior information about the features of an upcoming target facilitates sensory processing and speeds the initiation of both pursuit and saccades. Because the preparation of these eye movements is constrained by the speed of motor processing as well, facilitation of specific motor commands might also speed the initiation of pursuit and saccades. To test for such motor effects, we examined the effects of prior motor and sensory information on pursuit and saccadic latencies. METHODS. Human observers tracked one of two 2° gabor patches (2 cycles/deg), that were either stationary (saccade trials) or moving at 8°/sec (pursuit trials). Eye movements were recorded with a video-based tracker. Preceding target onset, either a sensory cue, a motor cue, both cues, or no cues were presented. Sensory cues provided either spatial or motion information. The motor cue was either the word “track” or “step”, indicating that either pursuit or a saccade, respectively, would be required by the upcoming target stimulus. RESULTS. Baseline latencies for pursuit and saccades were measured from trials with no cues (219ms & 303ms, respectively). Prior motor information alone had no effect on the latency of pursuit (220ms) and actually increased the latency of saccades (348ms). However, presenting both prior motor and sensory information decreased pursuit (162ms) and saccade latencies (211ms). Prior sensory information alone about spatial location produced smaller decreases in both pursuit (178ms) and saccade (225ms) latencies. Prior information about motion alone produced yet smaller decreases in the latency of pursuit (206ms) and increased saccade latencies (353ms). CONCLUSIONS. That motor cues influenced the initiation of pursuit and saccades only when combined with sensory cues suggests that the motor processing for eye movements can be facilitated but requires information about the likely location of the target and metrics of the movement.