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PubMedDate not supplied

Binocular depth perception following early experience with interocular torsional disparity.

The relationship between the behavioral and physiological consequences of rearing with optically induced cyclotropia was assessed. Beginning at the age of 4 weeks, kittens wore goggles that rotated the visual field in opposite directions in each eye for several hours each day over a period of several weeks. The amounts of interocular rotation were 0 deg (control), 16 deg, and 32 deg. Subsequently, they were tested to determine their monocular and binocular depth thresholds and, in some cases, visual acuity. In several kittens recordings were also made from the visual cortex. Binocular performance of all kittens in the 0-deg condition and three out of six kittens in the 16-deg condition was comparable to, although slightly lower than, that of normally reared kittens. In contrast, none of the 32-deg kittens showed any evidence of the binocular superiority that would suggest the presence of stereopsis. Extracellular unit recordings from the visual cortex confirmed our earlier results with goggle-reared kittens. In 16-deg kittens, the distribution of the cells' preferred interocular disparities (IOD) in receptive-field orientation showed a compensating shift so that the mean matched the experienced rotational disparity. In the 32-deg kittens, binocularity was greatly disrupted and there was no compensatory shift in the IOD distribution. Two 32-deg kittens were afforded 3 years of subsequent normal visual experience. Both the behavioral and the physiological findings were unaffected by normal visual exposure in adulthood. Control measurements of acuity indicated that any deficits in depth perception were not due to reduced spatial-resolution abilities. The data indicate that the kitten visual system is able to maintain functional binocularity sufficient to subserve a moderate level of stereoacuity with interocular rotations of up to at least 16 deg.

Animals↗
PubMed1986

Depth perception as a function of motion parallax and absolute-distance information.

The results of three experiments demonstrated that the visual system calibrates motion parallax according to absolute-distance information in processing depth. The parallax was created by yoking the relative movement of random dots displayed on a cathode-ray tube to the movements of the head. In Experiment 1, at viewing distances of 40 cm and 80 cm, observers reported the apparent depth produced by motion parallax equivalent to a binocular disparity of 0.47 degree. The mean apparent depth at 80 cm was 2.6 times larger than at 40 cm. In Experiment 2, again at viewing distances of 40 cm and 80 cm, observers adjusted the extent of parallax so that the apparent depth was 7.0 cm. The mean extent of parallax at 80 cm was 31% of that at 40 cm. In Experiment 3, distances ranged from 40 cm to 320 cm, and a wide range of parallax was used. As distance and parallax increased, the perception of a rigid three-dimensional surface was accompanied by rocking motion; perception of depth was replaced by perception of motion in some trials at 320 cm. Moreover, the mean apparent depths were proportional to the viewing distance at 40 cm and 80 cm but not at 160 cm and 320 cm.

Cues↗
PubMed1992

Depth perception of interfering periodic patterns: a possible contribution to disorientation on escalators.

Incongruous and illusory depth cues, arising from 'interference patterns' produced by overlapping linear grids at the edges of escalator treads, may contribute to the disorientation experienced by some escalator users, which in turn may contribute to the causes of some of the many escalator accidents which occur. The apparent depth of the interference pattern from the viewer is analysed in terms of the cues deriving from size and viewer motion. Both of these cues support the depth of the target being infinite. Preliminary observations are reported which confirm this analysis. Remedies for the problem are suggested. The possible contribution of this illusion to disorientation on escalators, due to misjudgment of depth, is compared with another recently reported factor which is due to stereoscopic miscorrespondence of periodic targets.

Accident Proneness↗
PubMed1978

Role of two-dimensional surface characteristics in pictorial depth perception.

The purpose of the present experiment was to test the hypothesis that flat surface information for the plane of projection is the essential difference between ordinary and pictorial perception. Adults were asked to make relative size judgments of pairs of squares and triangles placed and pictured at various distances. The conditions were: real scene controls, life-size slides and prints, and real scenes viewed through clear glass, textured glass, a screen and a 50-mm lens. The error rate was significantly lower with real scenes than with either slides or prints which did not differ. The control data for real scenes were used for comparison to test for the effects of interposed flat surfaces on size judgments of real scenes. Viewing real scenes through either a clear glass pane or a 50-mm lens increased the error rate two and one-half times that of the controls for real scenes. Neither textured glass nor a screen significantly affected error rate. Results were interpreted as supporting the hypothesis that information about a flat surface for the plane of projection is the critical variable determining the special character of picture perception.

Depth Perception↗
PubMed1990

Effects of brief monocular deprivation on binocular depth perception in the cat: a sensitive period for the loss of stereopsis.

The period of susceptibility for binocular depth vision was studied in kittens by subjecting them to periods of monocular deprivation beginning at different ages. In an initial study, we found that normally reared kittens can learn a depth-discrimination task much more rapidly when tested binocularly than monocularly, even when testing is begun as early at 30 d. In subsequent experiments, kittens were monocularly deprived by eyelid suture, following which their monocular and binocular depth thresholds were measured using the jumping-stand procedure. We obtained the following results: (1) When monocular deprivation is applied before the time of natural eye opening but is discontinued by no later than 30 d, there is very little effect on binocular depth thresholds. (2) When deprivation is begun at 90 d, binocular depth thresholds are unaffected. (3) When deprivation is begun between these two ages, the magnitude of the deficit varies with the period of deprivation and the age at which it begins. (4) By imposing brief (5 or 10 d) periods of deprivation, beginning at different ages, we were able to demonstrate that the peak of the sensitive period is between the ages of 35 and 45 d, with a fairly rapid decline in susceptibility outside those age limits. (5) Even with as little as 5 d of deprivation, substantial permanent deficits in binocular depth vision can be induced.

Animals↗
PubMed1988

Dynamic occlusion and motion parallax in depth perception.

Random-dot techniques were used to examine the interactions between the depth cues of dynamic occlusion and motion parallax in the perception of three-dimensional (3-D) structures, in two different situations: (a) when an observer moved laterally with respect to a rigid 3-D structure, and (b) when surfaces at different distances moved with respect to a stationary observer. In condition (a), the extent of accretion/deletion (dynamic occlusion) and the amount of relative motion (motion parallax) were both linked to the motion of the observer. When the two cues specified opposite, and therefore contradictory, depth orders, the perceived order in depth of the simulated surfaces was dependent on the magnitude of the depth separation. For small depth separations, motion parallax determined the perceived order, whereas for large separations it was determined by dynamic occlusion. In condition (b), where the motion parallax cues for depth order were inherently ambiguous, depth order was determined principally by the unambiguous occlusion information.

Attention↗
PubMed1975

Depth perception in the rat (Rattus Norvegicus): prepotency of three-dimensional over two-dimensional surfaces.

The descent behavior to two- and three-dimensional surfaces in a depth situation was measured and compared for 45-50 days-old hooded rats. When depth differences between surfaces were controlled, significantly more descents were made to three-dimensional than to the two-dimensional surface. The results suggest that a three-dimensional surface--more representative of an animal's natural terrain--provides a more informative environment for motion parallax than does a two-dimensional one.

Animals↗