Perception of Depth in Natural Scenes

[摘要] The role of disparity in depth perception has typically been studied using random-dot stereograms because they contain no monocular clues, thus isolating the responses to "pure disparity". Pure disparity rarely exists in the real world. Rather, disparity occurs in the context of several monocular depth cues. To study disparity processing in natural scenes, we compared visually evoked responses to 2D and 3D versions of the same scene that differed only in their disparity structure. Thirty natural scenes were drawn from a large set of natural image stereo-pairs (Burge et al., 2016 J. Vis) to ensure diversity of scene types and depth maps. The scenes mainly included outdoor settings with trees and buildings. Nineteen subjects (Mean age = 22.9, 8 males) viewed a sequential two-alternative temporal forced choice presentation of two different versions of the same scene (2D vs. 3D) interleaved by a scrambled image with the same power spectrum (4 images per trial, 750 ms each). Scenes were viewed orthostereoscopically at 3 meters through a pair of shutter glasses. After each trial, participants indicated with a key press which version of the scene was 3D. Performance on the discrimination was >90%. We compared 128 channel Visual Evoked Potentials elicited by 2D and 3D scenes using Reliable Component Analysis (Dmochowski Greaves and Norcia, 2015). Both scene types elicited responses with onset times of ~180 msec. The differential response between 2D and 3D scenes was maximal on mid-line electrodes over the occipital pole. Significant differences between responses to 2D and 3D scenes first emerged at around 200 msec. This suggests that approximately 20 additional msec are needed for the brain to begin the extraction of 3D structure from the disparity cues in natural scenes.

[学科分类] 眼科学