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Results for “Depth Perception”

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At least 1,117 records · Page 62Linked to original sources
PubMed2004

Asymmetry in the perception of motion-in-depth.

We investigated the anisotropic responses between the detection of motion toward and motion away from the observers with expanding/contracting shaded circles. Our experiments followed visual search paradigm with two exceptions: (1) the stimulus presentation time was fixed for 300 ms and (2) the mean error rates were adopted as a dependent variable. In Experiment 1, targets and distractors were defined by expanding (or contracting) convex/concave circles. Results of Experiment 1 suggested that the human visual system is more sensitive to expanding convex circles (which create the impression of approaching objects) than others. In Experiment 2, the targets and distractors were defined by expanding (or contracting) step gradient (top-lighting/bottom-lighting) circles. The results of Experiment 2 suggest that the anisotropy for the perception of motion-in-depth should not be caused by change of luminance polarity but by change of shading cue.

Adolescent↗
PubMed1993

Surface segmentation mechanisms and motion perception.

Two studies are presented which explore how depth information is determined from conditions of transparency and whether this information combines with other depth information to determine the segmenting of motion information on the basis of likely surface boundaries. The first study explored how binocular disparity combines with monocular depth cues associated with transparency to determine whether subjects see one or multiple surfaces in depth in static displays. When transparency provided a depth cue that was consistent with binocular disparity, depth discrimination thresholds were at normal levels. However, if transparency was inconsistent with the binocular disparity, depth discrimination thresholds were elevated, indicating that subjects had difficulty seeing distinct surfaces lying in separate depth planes. Moreover, threshold elevations were found to correspond to the reductions in contrast between the intersecting contours of the stimulus, suggesting that the strength of perceived depth from transparency is the result of attenuated responses from competing contrast sensitive T-junction mechanisms responsible for the detection of opaque occlusion. A second experiment explored whether the grouping of local motion signals relied on surface interpretations that result from the interaction of transparency and disparity. Surface interpretations were manipulated in moving plaids by combining transparent layering and binocular disparity to show that the motion arising from contours is grouped together (pattern motion) when these cues support the existence of a single surface, and is segregated (component motion) when they support separate surfaces. When these cues were consistent, only small disparity differences were required for the gratings to appear as separately moving surfaces. However, when they were inconsistent, greater disparities were required (about a factor of 2 greater). Taken together, these studies demonstrate that the grouping of local motion information is not resolved within the motion system alone. Information seemingly unrelated to motion processing, namely surface segmentation cues, is used to determine whether or not motion information arising from various contours is pooled together to determine a single motion.

Cues↗
PubMed2005

Visual depth processing in Williams-Beuren syndrome.

Patients with Williams-Beuren Syndrome (WBS, also known as Williams Syndrome) show many problems in motor activities requiring visuo-motor integration, such as walking stairs. We tested to what extent these problems might be related to a deficit in the perception of visual depth or to problems in using this information in guiding movements. Monocular and binocular visual depth perception was tested in 33 patients with WBS. Furthermore, hand movements to a target were recorded in conditions with and without visual feedback of the position of the hand. The WBS group was compared to a group of control subjects. The WBS patients were able to perceive monocular depth cues that require global processing, but about 49% failed to show stereopsis. On average, patients with WBS moved their hand too far when no visual feedback on hand position was given. This was not so when they could see their hand. Patients with WBS are able to derive depth from complex spatial relationships between objects. However, they seem to be impaired in using depth information for guiding their movements when deprived of visual feedback. We conclude that the problems that WBS patients have with tasks such as descending stairs are not due to an inability to judge distance.

Adolescent↗
PubMed2002

Interactions between chromatic- and luminance-contrast-sensitive stereopsis mechanisms.

It is well known that chromatic information can assist in solving the stereo correspondence problem. It has also been suggested that there are two independent first-order stereopsis mechanisms, one sensitive to chromatic contrast and the other sensitive to luminance contrast (Vision Research 37 (1997) 1271). Could the effect of chromatic information on stereo correspondence be subserved by interactions between these mechanisms? To address this question, disparity thresholds (1/stereoacuity) were measured using 0.5 cpd Gabor patches. The stimuli possessed different relative amounts of chromatic and luminance contrast which could be correlated or anti-correlated between the eyes. Stereoscopic performance with these compound stimuli was compared to that with purely isoluminant and isochromatic stimuli at different contrasts. It was found that anti-correlated chromatic contrast severely disrupted stereopsis with achromatic stimuli and that anti-correlated luminance contrast severely disrupted stereopsis with chromatic stimuli. Less dramatic, but still significant, was the improvement in stereoacuity obtained using correlated colour and luminance contrast. These data are consistent with there being positive and negative interactions between chromatic and achromatic stereopsis mechanisms that take place after the initial encoding of disparity information, but before the extraction of stereoscopic depth. These interactions can be modelled satisfactorily assuming probability summation of depth sign information between independent mechanisms.

Color Perception↗
PubMed1981

Pursuit eye movements and the depth-movement phenomenon in dynamic visual noise.

The ability to generate voluntary pursuit eye movements in the absence of retinal-contour motion cues was assessed on the basis of observers' perceptions of depth and motion when they viewed dynamic visual noise with a filter over one eye. The results indicated that the depth-movement phenomenon yielded robust pursuit with the velocity an inverse function of filter density. These data suggest that retinal-contour motion cues are not necessary and that perceived motion is sufficient to drive pursuit.

Cues↗
PubMed2001

Functional organization of macaque V3 for stereoscopic depth.

Recordings were made from single and small groups of cells in prestriate area V3 of the visual cortex of the Cynomolgus macaque (Macaca fascicularis). The majority of cells in V3 were selective for orientation and stereoscopic depth, these cells being segregated into two sets of functionally distinct columns. Orientation columns in V3 have been previously demonstrated; here we show that V3 also contains columns of segregated disparity-selective cells. On the basis of its cellular properties, functional organization, and intra-cortical connections, we propose that V3 contributes to the processing of stereoscopic depth information and that the parietal areas to which it projects use this information for the analysis of object depth and three-dimensional form.

Animals↗
PubMed1979

Ontogenetic study of the Miwh gene in mice.

Ontogenetic and adult behavioral tests were conducted on an extreme non-agouti strain of mice carrying the Miwh mutation. Except for startle response, no significant differences were seen in any aspect of the preweaning reflex and neuromuscular tests. The lack of startle response seen in Miwh/Miwh and Miwh/+ mice can be attributed to abnormalities found in the inner ear of these genotypes. Among adult mice, significant differences were found in the open field and visual cliff tests.

Animals↗