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At least 199 records · Page 11Linked to original sources
PubMed1986

Binocular depth perception in the pigeon.

By means of a discrete-trial simultaneous discrimination procedure, pigeons were trained to respond differentially to visual arrays that were identical except that one of them contained a circle displaced in depth when viewed stereoscopically. Performance was severely disrupted when one eye was occluded. The monocular deficit was peculiar to the depth task, inasmuch as no such decrement was seen on a pattern discrimination. The results imply that presence of the displaced circle was discriminated on the basis of a binocular cue. It was also found that pigeons could discriminate the direction of the displacement. Discrimination of depth was independent of the global form and still occurred when elements of the array were randomly displaced in depth. Performance was not disrupted when the absolute convergence angle of the depth stimulus was changed. The cue that consistently accounted for the behavior seen was the detection of the relative angles of convergence--that is, the retinal disparity of the two planes in depth. Thus, despite the lateral position of the eyes of the pigeon, a small binocular field mediates the binocular discrimination of near objects in depth.

Animals↗
PubMed1979

Motion parallax as an independent cue for depth perception.

The perspective transformations of the retinal image, produced by either the movement of an observer or the movement of objects in the visual world, were found to produce a reliable, consistent, and unambiguous impression of relative depth in the absence of all other cues to depth and distance. The stimulus displays consisted of computer-generated random-dot patterns that could be transformed by each movement of the observer or the display oscilloscope to simulate the relative movement information produced by a three-dimensional surface. Using a stereoscopic matching task, the second experiment showed that the perceived depth from parallax transformations is in close agreement with the degree of relative image displacement, as well as producing a compelling impression of three-dimensionality not unlike that found with random-dot stereograms.

Cues↗
PubMed1995

Natural problems for stereoscopic depth perception in virtual environments.

The use of virtual reality (VR) display systems has escalated over the last 5 yr and may have consequences for those working within vision research. This paper provides a brief review of the literature pertaining to the representation of depth in stereoscopic VR displays. Specific attention is paid to the response of the accommodation system with its cross-links to vergence eye movements, and to the spatial errors that arise when portraying three-dimensional space on a two-dimensional window. It is suggested that these factors prevent large depth intervals of three-dimensional visual space being rendered with integrity through dual two-dimensional arrays.

Accommodation, Ocular↗
PubMed1976

Depth perception after infant and adult visual neocortical lesions in light- and dark-reared rats.

In 2 experiments the behavior of light- and dark-reared infant- and adult-operated striate rats were compared at 20-160 days of age on a visual cliff apparatus in which the depth of the deep side could be varied. Differential depth thresholds revealed that depth discriminative ability did not develop normally following removal of the striate cortex in infancy. Further, infant-operates who were reared in darkness following their operations performed less well than their light-reared, infant-operated counterparts. The infant-operated animals, regardless of their postoperative rearing condition, performed significantly better than did adult-operated animals after comparable post-operative recovery periods and testing. The results are discussed in terms of further specification of the role played by age of operation and by the interaction between visual experience and age of operation.

Age Factors↗
PubMed1980

Depth perception in moving line patterns.

By means of a computer system, the two-dimensional projections of a three-dimensional random wire figure, rotated clockwise (CW) or counterclockwise (CCW) about the vertical axis, were produced and displayed on a CRT. Generally the stimulus display appeared as an object rotating in depth, changing direction of movement frequently from clockwise rotation to counterclockwise, and vice versa. In the experiment, the three subjects observed the displays of three different types of projection, two polar projections and a parallel one. They were instructed to judge the direction of the seen motion and asked to report it using the button-switches. Both duration of the rotation perceived in either direction and frequency of the apparent reversals between those two were measured from the output sheets of a pen-recorder. The results showed the effects of the type of projection. (1) The veridical motions were perceived more continuously and durably in the polar projections than in the parallel one, (2) the opposite relation was found with the nonveridical motions, and (3) the reversals of moving direction were seen more frequently in the parallel projection than in the polar ones.

Adult↗
PubMedDate not supplied

The role of eye accommodation in the depth perception of common toads.

Distance estimation in prey catching was as exact in monocular toads (Bufo bufo (L.)) as in binocular ones. Application of Atropine or Miotic had no significant effect on binocular animals, whereas in monocular toads it made accurate distance estimation impossible. The accommodative state of the eye is decisive for depth estimation of monocular, but not of binocular toads.

Accommodation, Ocular↗
PubMed1988

An occlusion-related mechanism of depth perception based on motion and interocular sequence.

Objects occlude other objects in natural scenes, and this occlusive relationship increases the spatio-temporal complexity of sensory inputs to the two eyes, especially when objects are moving. We ask whether the visual system can employ clever strategies which make use of real-world constraints on inputs to the eyes to determine the depth of objects. Employing psychophysical methods, we found that occlusion-related geometric rules, which constrain the relationship between the direction of motion and the order and asynchrony of eyes, are implemented at early stages of cortical visual processing.

Depth Perception↗
PubMed1989

Stereoscopic depth perception by static stereo-deficient observers in dynamic displays with constant and changing disparity.

The performance of 11 static stereo-deficient subjects and 11 static stereo-normal subjects was compared on two types of dynamic stereo displays--one where disparities were constant during motion and one where disparities changed continuously. Computer-generated displays simulating horizontal motion of figures at different depths or rotation of figures about a vertical axis were viewed through a Brewster stereoscope. About one-half of the subjects in our static stereo-deficient sample were able to make depth judgments on the basis of disparity in both types of dynamic displays. The clinical feature which appeared to distinguish those static stereo-deficient subjects who could use disparity information in dynamic displays from those who could not was early onset constant strabismus. These results indicate that a complete evaluation of stereo ability should include tests with dynamic displays, possibly including both constant and changing disparities.

Adult↗
PubMed1967

Traffic signals and depth perception.

Automobiles approaching red traffic signals at night appear to go beyond them when viewed from some distance to the rear. The phenomenon is doubly illusory because the higher of two objects has been presumed to appear more distant. The illusion is probably limited to small visual angles (about 2 degrees).

Automobile Driving↗
PubMedDate not supplied

Depth perception and evoked brain activity: the influence of horizontal disparity and visual field location.

The perception of dynamic random-dot stereograms (RDS) depends on the physiological fusion of horizontally disparate binocular visual input. Thus, the use of RDS offers the possibility to study selectively cortical processing of visual information in man. We investigated the influence of horizontal disparity on the scalp topography of RDS evoked brain activity in 33 healthy subjects. Stereoscopic checkerboard patterns were presented in the center or lateralized in the left or right visual field with horizontal disparities changing at temporal frequencies of six or eight depth reversals/s using different disparity values ranging from 3.5 to 28 min of arc. In 11 subjects evoked potential fields were recorded from 16 electrodes, and 21 subjects participated in 30-channel recordings with electrodes located over the parietal and occipital brain areas. Stimulation frequency-related brain activity was obtained with all disparity values; however, with large or small disparities the potential field strength decreased significantly while largest responses were obtained with intermediate disparities. Significant differences were observed in RDS evoked brain activity when central and lateralized stimulus locations were compared. With lateral stimuli (extending from the fovea to 17.1-deg eccentricity) maximal amplitudes were obtained at larger disparities than with central stimuli. In addition there were pronounced differences between brain activity evoked with stimuli presented in the left or right visual field; however, there were very similar evoked potential signals recorded from electrodes located over the left and right hemispheres. Our findings indicate that the processing of disparity information with lateralized stimuli is different from the processing in the center of the visual field. In addition, lateralized stimulation yields a significant disparity tuning mainly with stereoscopic targets occurring to the right from the fixation point (but not with stimuli to the left) suggesting a functional difference between the visual half-fields.

Adult↗
PubMed1996

Stereoscopic depth perception and vertical disparity: neural mechanisms.

The additivity assumption relates to the various stereo-disparity components in the vertical and horizontal meridians, each of which is assumed to be independent of the other, with the total disparity in each dimension being the linear sum of the separate components. Information about the position of the eyes provided by the corollary discharge leads to compensatory changes in the lateral geniculate nuclei whereby the angle of gaze disparity component at retinal level is offset by equal and opposite changes at geniculate level. These geniculate changes concern only eye position. Changes in the retinal images such as those produced by lenses (i.e. induced effect) are passed on to the cortex without modification at the geniculate level. Discrimination of the local depth disparity component can be achieved by subtracting the local vertical eccentricity component from the total horizontal disparity.

Depth Perception↗