Schor C M, Edwards M, Sato M
School of Optometry, University of California, 360 Minor Hall, Berkeley, CA 94720-2020, USA.
Vision Res. 2001 Sep;41(20):2555-67. doi: 10.1016/s0042-6989(01)00155-9.
Stereopsis is the sense of depth derived from binocular disparities that are formed between targets that are matched between the two retinal images. Binocular matches for sustained stereopsis are based on similarity of orientation, spatial frequency and contrast of the two retinal images whereas matches for transient stereopsis depend on these parameters to a very limited extent. In this investigation we have tested the possibility that transient stereopsis forms matches between objects of similar overall size. The tuning of sustained and transient stereopsis to contrast-envelope size was investigated by presenting narrow-band Gabor targets of unequal size to the two eyes. Bandwidth for envelope-size tuning was estimated from the range of dichoptic size-differences over which stereo performance remained above chance level. An equal bandwidth of 2 octaves was found for the sustained and transient stereo systems when stimulated with parallel orientation Gabors that subtended a small disparity. Sustained-stereo performance with orthogonal carriers was reduced with large envelope sizes. Bandwidth of the transient stereo system increased to 3 octaves when tested with a larger disparity stimulus and it was independent of carrier orientation. Reducing the contrast of the larger-size Gabor improved transient-stereo performance from near chance (48-58%) to 85-95%. Thus the bandwidth for envelope-size tuning is much broader than indicated with equal physical contrast stimuli. The observed tuning to envelope size, while broad, is tighter than that observed for carrier spatial-frequency [Vis. Res. 38 (1998) 3057], carrier orientation [Vis. Res. 39 (1999) 2717] and contrast polarity [Vis. Res. 39 (1999) 4010] of the stimulus. Thus it would appear that envelope size and, to a greater extent, temporal synchrony of the dichoptic stimuli [Perception 24 (1995) 33] are the primary means for selecting matched binocular inputs for transient stereopsis.
立体视觉是从双眼视差中获得的深度感知，这种视差是在两个视网膜图像中匹配的目标之间形成的。持续立体视觉的双眼匹配基于两个视网膜图像的方向、空间频率和对比度的相似性，而瞬态立体视觉的匹配在很大程度上仅依赖于这些参数。在本研究中，我们测试了瞬态立体视觉在总体尺寸相似的物体之间形成匹配的可能性。通过向双眼呈现大小不等的窄带Gabor目标，研究了持续和瞬态立体视觉对对比度包络大小的调谐。包络大小调谐的带宽是根据双眼大小差异的范围来估计的，在这个范围内立体视觉性能仍高于随机水平。当用具有小视差的平行方向Gabor刺激时，持续和瞬态立体视觉系统的带宽均为2倍频程。当使用正交载波时，大的包络大小会降低持续立体视觉的性能。当用更大的视差刺激进行测试时，瞬态立体视觉系统的带宽增加到3倍频程，并且与载波方向无关。降低较大尺寸Gabor的对比度可将瞬态立体视觉性能从接近随机水平（48 - 58%）提高到85 - 95%。因此，包络大小调谐的带宽比同等物理对比度刺激所显示的要宽得多。观察到的对包络大小的调谐虽然较宽，但比对刺激的载波空间频率[《视觉研究》38 (1998) 3057]、载波方向[《视觉研究》39 (1999) 2717]和对比度极性[《视觉研究》39 (1999) 4010]的调谐更紧密。因此，似乎包络大小以及在更大程度上双眼刺激的时间同步性[《感知》24 (1995) 33]是为瞬态立体视觉选择匹配的双眼输入的主要手段。
