Abstract
More than half of typically sighted observers have difficulty perceiving three-dimensional (3D) motion. Specifically, these individuals are unable to discriminate the direction of motion-in-depth (i.e., "towards" vs. "away") within spatially restricted regions of the visual field. This deficit appears to result from impairments in the integration of binocular motion signals. Even though the perceptual experience of 3D motion is absent, the sensory signals required for 3D motion perception are available, as evidenced by normal sensitivity to frontoparallel motion and static binocular disparity. As such, we previously characterized this deficit as an agnosia specific to 3D motion. Here we extend these findings by investigating the contribution of monocular cues to 3D motion perception in both affected and unaffected individuals. Participants sat 90 cm from a display containing dots moving either towards or away from them within a simulated cylindrical volume (1.5° diameter, 12 cm depth). On each trial, a 3D motion stimulus appeared in one of 40 locations arranged in a spoke-wheel pattern with eccentricity ranging from 1.5° to 7.5°. Stimuli contained monocular, binocular, or both cues to 3D motion. Sensitivity to each cue was assessed by varying dot motion coherence. Our results show considerable variability in the sensitivity to monocular and binocular cues across observers. However, all observers integrate the two cues near-optimally. Furthermore, the previously established deficit in perception of 3D motion appears to be specific to stimuli containing only binocular cues. Perception based on monocular cues seems to be unaffected. These results show that the deficit results from a spatially restricted impairment in the integration of binocular cues to motion-in-depth. In future studies, we aim to uncover the neural basis of this deficit in 3D visual motion perception using brain imaging (fMRI/DTI) in humans, and neural recordings in non-human primates
Meeting abstract presented at VSS 2017