PubMed · 7079100
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K Prazdny. 1982. Blur patterns: a comment.. https://doi.org/10.3758/bf03206220
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The view of the world from different perspectives provided by the two eyes is used by the human visual system to compute the relative distances and solid shapes of objects. However, the traditional theory of binocular disparity takes little account of the fact that a moving target will stimulate many different sets of disparate points in the two eyes with a range of temporal delays. Here we show that stereoacuity for periodic grating is not degraded by velocities of up to 640 degrees s-1 provided that they do not move at a greater rate than 30 cycles s-1. The minimum detectable spatial phase difference between the eyes was equivalent to a spatial phase difference of about 5 degrees and an interocular temporal delay as small as 450 microseconds. We suggest that stereopsis for moving targets is accomplished by neurons having a spatial-temporal phase shift in their receptive fields between the eyes.
In order to investigate the extent of the local connections subserving contour integration across depth, we measured performance for detecting the continuity of a path of Gabor elements distributed in depth and embedded in a three-dimensional field of random background elements. The results show that performance cannot be explained in terms of monocular performance and that contour information is not limited to single disparity planes. Path detection does indeed involve the integration of information across different, very disparate depth planes. The rules which emerge are in general similar to that already described in the two-dimensional case in as far as orientation and disparity are important. Unlike the two-dimensional case, three-dimensional integration operates over relatively large three-dimensional distances.
To interpret the projected image of a moving object, the visual system must integrate motion signals across different image regions. Traditionally, researchers have examined this process by focusing on the integration of equally ambiguous motion signals. However, when the motions of complex, multi-featured images are measured through spatially limited receptive fields, the resulting motion measurements have varying degrees of ambiguity. In a series of experiments, we examine how human observers interpret images containing motion signals of differing degrees of ambiguity. Subjects judged the perceived coherence of images consisting of an ambiguously translating grating and an unambiguously translating random dot pattern. Perceived coherence of the dotted grating depended upon the degree of concurrence between the velocities of the grating terminators and dots. Depth relationships also played a critical role in the motion integration process. When terminators were suppressed with occlusion cues, coherence increased. When dots and gratings were presented at different depth planes, coherence decreased. We use these results to outline the conditions under which the visual system uses unambiguous motion signals to interpret object motion.