Callista Dyer¹ (), Victor Rodriguez-Lopez², Johannes Burge^1,3,4; ¹Department of Psychology, University of Pennsylvania, PA, ²Institute of Optics, Spanish National Research Council, IO-CSIC, ³Neuroscience Graduate Group, University of Pennsylvania, PA, ⁴Bioengineering Graduate Group, University of Pennsylvania, PA

Differential image motion underlies motion parallax, an important cue for the perception of depth and 3D structure. Eye movements affect the pattern of image motion. It is well-appreciated that eye movements can alter the perceived speed of moving stimuli (Freeman et al., 2010). Here, we examine how eye movements alter the perception of depth from stimuli without and with differential motion, in the presence of interocular delays. The stimulus consisted of two dichoptically-presented strips of horizontally moving bars–one above and one below fixation–that moved either in the same or in opposite directions. The fixation target was stationary, moved left, or moved right. The task was to report–while maintaining fixation–the depth order of the bars relative to fixation. Interocular delays were induced by reducing the luminance in one eye. Psychometric functions were measured. The aim was to find the onscreen delay that nulled the depth percept. These critical onscreen delays should have the same magnitude and opposite sign as the neural delay. Without differential target motion (i.e. both bars move in the same direction), the results are straightforward: target motion causes illusions with stationary fixation (gain=0.0), smooth pursuit (gain=1.0) eliminates them, and anti-pursuit (gain=-1.0) accentuates them. These results suggest that retinal image motion is required for neural disparities to result from interocular delays. In the presence of differential target motion, the pattern of results is more complicated and unexpected. With differential target motion, leftward eye movements produced depth illusions that required critical onscreen advances of the left-eye image, and vice versa. It is as if leftward eye movements delay left-eye visual information processing, and rightward eye movements delay right-eye visual information processing. We discuss attempts to understand the patterns in the data.

Acknowledgements: This work was supported by the National Eye Institute and the Office of Behavioral and Social Sciences Research, National Institutes of Health Grant R01-EY028571 to J.B., and by the National Institutes of Health Vision Training Program T32EY007035 to C.D