Abstract
We successfully interact with moving objects while our eyes actively receive motion information in dynamic environments. Our sensorimotor system realigns gaze direction based on the integrated outputs of local motion sensors across the visual field. We examine the relationship between oculomotor and perceptual estimates of the speed and direction of apertured local motion signals. Eight observers viewed 363±26 trials, in which randomly-oriented Gabors (carrier=0.5 cycle/°, envelope σ=0.25°, contrast=100%) were presented within a 10° radius field. After central fixation for 700-1100msec, motion in a global direction (random across trials) was generated by drifting the carrier, the envelope or both at 5, 10 or 15°/sec for 500-700msec and observers were free to make eye movements. They then adjusted the speed and direction of Gaussian-windowed (σ=1.5°) 1/F noise to match that of the moving target. Matching performance was estimated by bias between the absolute angular and speed difference between the global direction of the Gabors and the match stimuli. Perceptual biases for both global speed and direction were dependent on the motion signal type. Perceptual biases of carrier motion were significantly different from that of the envelope motion only (p<0.001) and that of carrier+envelope motion (p<0.001). Eye movement patterns differed between the motion signal types. The carrier+envelope motion produced the most smooth pursuit eye movements that manifest significant direction biases during the initiation of smooth pursuits, as measured by absolute velocity toward the direction of the Gabors. These results identify differences between perceived motion and eye movements that depend on local motion signals and challenge simple models of global motion integration.