The Extra-retinal Contribution to the Perception of Motion in Depth

In natural settings, our eyes tend to track interesting or dangerous objects moving towards us. This complicates the relationship between an object's motion and the binocular retinal projection of its motion. To perceive the object's motion, the brain should take eye movement information into account. This could be done using retinal cues (the slip of static scene structures) or extra-retinal cues (e.g. copies of motor commands). Previous studies have found that extra-retinal cues provide a very poor cue to eye rotation (Erkelens Collewijn, Vision Research, 1985, 583-588; Regan et al., Invest Opthal Vis Sci, 1986, 584-597) thus suggesting that extra-retinal cues are not used to perceive motion-in-depth. Here, we re-evaluate the brain's use of extraretinal cues in 3D motion perception. We employ conditions designed to isolate retinal cues and extra-retinal cues to motion-in-depth. In contrast to previous reports, we nd that observers can use extra-retinal cues to make accurate motiondiscriminations. We report that extra-retinal signals provide reliable information about eye rotations that is used to perceive 3D motion